Opinion On This Tank Please

[greengoddess]

Hi,

I am in the process of hunting for a new tank for my two fantail goldfish. I made the mistake of putting thm both in a 25 litre tank. After being on this forum I now know that I need a much larger tank, at least 150 litres.

I have limited space in my living room (84cm gap in an alcove) but I have found this tank: click here

It's 220 litre but it's a cube shape and will therefore fit into my room nicely. However, 2 things concern me:

1. Although the tank is 220 litres, will the actual shape of it be a disadvantage to my fish when they mature and become large? With a standard 220 litre rectangular tank, fish can swim lengthways for quite a distance. With a cube tank this distance is shorter although the height and depth are greater.

2. I plan on keeping my two goldfish plus perhaps some smaller fish (not goldfish) and an algae eater or two in this tank. I don't want to have to go out and buy another even larger tank in a few years because my fish have outgrown it. So my questions is: Will this 220 litre tank be suitable for the life of my goldfish (assuming they live long happy lives) or will I need to go and buy a 300 or 400 litre tank at some point?

 

[VaegaVic]

Hi,
Hello
I am in the process of hunting for a new tank for my two fantail goldfish. I made the mistake of putting thm both in a 25 litre tank. After being on this forum I now know that I need a much larger tank, at least 150 litres.
Congrats on learning that, most people either don't want to learn or don't care. You should be proud of yourself.
I have limited space in my living room (84cm gap in an alcove) but I have found this tank: click here
Lovely.
It's 220 litre but it's a cube shape and will therefore fit into my room nicely. However, 2 things concern me:

1. Although the tank is 220 litres, will the actual shape of it be a disadvantage to my fish when they mature and become large? With a standard 220 litre rectangular tank, fish can swim lengthways for quite a distance. With a cube tank this distance is shorter although the height and depth are greater.

Generally yes, the longer the tank the better for G-fish, but 220 litres should make up for this nicely. The problem you'll have is trying to find a tank that big for under a metre, it normally can't be done. The fish would be much better off in the 220L square than a 25L rectangle, so anything is an upwards move IMO.

2. I plan on keeping my two goldfish plus perhaps some smaller fish (not goldfish) and an algae eater or two in this tank. I don't want to have to go out and buy another even larger tank in a few years because my fish have outgrown it. So my questions is: Will this 220 litre tank be suitable for the life of my goldfish (assuming they live long happy lives) or will I need to go and buy a 300 or 400 litre tank at some point?

With G-fish, I would normally advise a species only tank, reason being is that there isn't enough room for anything else, simply. Small fish might get eaten or even nip the G-fish, where as bigger fish require more room. You could possibly go with shrimp for the algae eaters as they are quick enough to avoid the lumbering advances of fancy goldfish.

I hope this gives you a hand. However, I personally would see if the LFS would take the fish back, buy the big tank and then turn it tropical. Tropical is so much easier to look after, and would give you exactly what you want - colour, substance and beauty.
One word of advice, just make sure you read up on cycling your tank.

 

[greengoddess]

Thanks VaegaVic,

The other problem I have is that there is NO WAY these two goldfish are going anywhere. They belong to my two kids (aged 3 and 7) and we have all fallen in love with them. On top of that, I would really like to add a bit of variety to the new tank so I don't just have two big goldfish lumbering around in it. I do have the option of putting the tank into another room with plenty of space (possibly up to a 450 litre bow fronted tank) but my living room alcove would be preferable. I know my requests aren;t ideal but that's the situation I'm in and it ain't changing

 

[JenCliBee]

Thanks VaegaVic,

The other problem I have is that there is NO WAY these two goldfish are going anywhere. They belong to my two kids (aged 3 and 7) and we have all fallen in love with them. On top of that, I would really like to add a bit of variety to the new tank so I don't just have two big goldfish lumbering around in it. I do have the option of putting the tank into another room with plenty of space (possibly up to a 450 litre bow fronted tank) but my living room alcove would be preferable. I know my requests aren;t ideal but that's the situation I'm in and it ain't changing

You have two options then really, buy a bigger tank and keep it cold water or have two tanks.

The goldfish will be more than fine in a 450 litre with room to add maybe a couple more but the waste then produced will need a big powerful external filter. Goldfish can get huge, especially common goldfish and adding your normal run of the mill tropical will usually end in them been eaten, not to mention they will require a heated tank which the goldfish shouldn't ideally be kept in.

I think if one tank is obtained it will be either keep it cold water or rehome the fish and go tropical.

 

[VaegaVic]

Haha, fair enough, just thought I'd offer.

In that case then, I can give you a few species of fish that can live in temperate conditions:

http/www.theaquariumwiki.com/Caridina_multidentata
(Shrimp I mentioned)

http/www.theaquariumwiki.com/Beaufortia_kweichowensis
(Hillstream Loach, generally prefers fast moving water so make sure there is an area of that.)

http/www.theaquariumwiki.com/Aphyocharax_anisitsi
http://www.theaquariumwiki.com/Aphyocharax_anisitsi(Bloodfin Tetra, can be very nippy so needs a large shoal, wouldn't be on my list of priorities)

http/www.theaquariumwiki.com/Apple_Snail
http://www.theaquariumwiki.com/Apple_Snail(Lovely community snail for eating algae, you can find a rainbow of colours these days)

http/www.theaquariumwiki.com/Asolene_spixi
http://www.theaquariumwiki.com/Asolene_spixi(Same as above)

http/www.theaquariumwiki.com/American_Flag_Fish
http://www.theaquariumwiki.com/American_Flag_Fish(Can be a tad nippy with other fish, best kept in species tanks, although I have seen them kept with larger g-fish)

http/www.theaquariumwiki.com/Fundulopanchax_sjostedti
http://www.theaquariumwiki.com/Fundulopanchax_sjostedti(Absolutely stunning, needs to be with larger fish)

http/www.theaquariumwiki.com/Paradise_fish
http://www.theaquariumwiki.com/Paradise_fish(See above, but mix a bit of american flag in)

http/www.theaquariumwiki.com/Danio_choprae
(Absolutely gorgeous, but needs a large group to prevent nipping)
http://www.theaquariumwiki.com/Danio_choprae
http/www.theaquariumwiki.com/Corydoras_paleatus
(Dear..god..yes! Buy these, they are fantastic, keep the bottom of the tank clean, ideally sand if you can, whilst looking gorgeous, they could even breed in your tank. They are also commonly available and shouldn't cost you more than £3 a fish.)


I really hope that gives you a hand, it took me a few minutes to write and research that all, but I hope it opens up your options a bit more!

If you need anything, don't be afraid to ask!

 

[VaegaVic]

Thanks VaegaVic,

The other problem I have is that there is NO WAY these two goldfish are going anywhere. They belong to my two kids (aged 3 and 7) and we have all fallen in love with them. On top of that, I would really like to add a bit of variety to the new tank so I don't just have two big goldfish lumbering around in it. I do have the option of putting the tank into another room with plenty of space (possibly up to a 450 litre bow fronted tank) but my living room alcove would be preferable. I know my requests aren;t ideal but that's the situation I'm in and it ain't changing

You have two options then really, buy a bigger tank and keep it cold water or have two tanks.

The goldfish will be more than fine in a 450 litre with room to add maybe a couple more but the waste then produced will need a big powerful external filter. Goldfish can get huge, especially common goldfish and adding your normal run of the mill tropical will usually end in them been eaten, not to mention they will require a heated tank which the goldfish shouldn't ideally be kept in.

I think if one tank is obtained it will be either keep it cold water or rehome the fish and go tropical.

I both agree and disagree with this.
Filter, yes, the bigger the better. Goldfish, yes, they can get massive.
But only 2 options? There are always more!
Goldfish can survive happily up to about 24C, although I would never recommend it.

Green my love, you could buy 2 tanks, but for a beginner, I can assure you that you will get very overwhelmed very quickly. Stick with the one for the time being, the bigger the better, but always remember: The bigger the tank, the more maintenance is needed and the more money to throw at it.

Go with the cube, add some temperate fish, the corys I suggested will be absolutely perfect, along with a couple of snails, shrimp and what not. Learn from that tank and if you decide that it's worth it (in terms of your time, not pennies) THEN buy the bigger tank.

 

[JenCliBee]

The higher them temp, the faster there growth rate and metabolism vastly increases, which entails more waste, quite often bigger fish etc etc.

You will need a big external filter, not bigger the better, to filter a 450 litre tank you will need a filter that can cope with it, even a fx5 probably would struggle with a fully stocked tank with goldfish in.

I noticed you have fantails(fancy goldfish) is this definitely what you have?, common goldfish(if that is what they are) will limit to the fish suggested above. The danios and bloodfins will be eaten and possible the cory's damaged from trying to be eaten. the hillstream loach isn't really a suitable tank mate for goldfish, they require different conditions ideally to keep them happy. The fin nippers if the goldfish are fantails are just a complete no no, the fins will just be far to tempting for them. Shrimp i wouldnt imagine lasting to long in the tank tbh either, goldfish maywell be slow slower but trust me they will catch shrimp and will devour very easily.

I cant comment on the other fish suggested becasue i don't know anything about them.

I also and this is just personal think that a 2 foot cube tank isnt big enough for goldfish, the 220 litres is fine but a tank with more 'lengh' will be far more ideal than a tank that just has the volume of water.

 

[VaegaVic]

The higher them temp, the faster there growth rate and metabolism vastly increases, which entails more waste, quite often bigger fish etc etc.

You will need a big external filter, not bigger the better, to filter a 450 litre tank you will need a filter that can cope with it, even a fx5 probably would struggle with a fully stocked tank with goldfish in.

I noticed you have fantails(fancy goldfish) is this definitely what you have?, common goldfish(if that is what they are) will limit to the fish suggested above. The minnows and bloodfins will be eaten and possible the cory's damaged from trying to be eaten. the hillstream loach isn't really a suitable tank mate for goldfish, they require different conditions ideally to keep them happy. The fin nippers if the goldfish are fantails are just a complete no no, the fins will just be far to tempting for them. Shrimp i wouldnt imagine lasting to long in the tank tbh either, goldfish maywell be slow slower but trust me they will catch shrimp and will devour very easily.

I cant comment on the other fish suggested becasue i don't know anything about them.

I also and this is just personal think that a 2 foot cube tank isnt big enough for goldfish, the 220 litres is fine but a tank with more 'lengh' will be far more ideal than a tank that just has the volume of water.

Yep, completely agree with all of that, I wasn't disputing what you said in the first place.
All I was saying is that there are always more options.
The danios and tetras, as I said, weren't on my list of priorities, but I thought I'd include them just to show how small the list of suitable tank mates was, and what to avoid.
As I said with the hillstream loach, needs fast flowing water, you could replicate with powerheads, and it will be easier in the cube tank as you won't have the power head aimed all the way along the tank, just a section.
The corys should be perfectly fine as they can reach 3", way too big for even a fully grown G-fish to eat.

I've always found that with G-fish, if they can't fit it in their mouth, they generally leave it alone. Of course this is personal experience and should be taken with a pinch of salt.
I've also found that if the fish are introduced when small, they don't have a problem with them, exactly the same as Angels with neons.

 

[JenCliBee]

The higher them temp, the faster there growth rate and metabolism vastly increases, which entails more waste, quite often bigger fish etc etc.

You will need a big external filter, not bigger the better, to filter a 450 litre tank you will need a filter that can cope with it, even a fx5 probably would struggle with a fully stocked tank with goldfish in.

I noticed you have fantails(fancy goldfish) is this definitely what you have?, common goldfish(if that is what they are) will limit to the fish suggested above. The minnows and bloodfins will be eaten and possible the cory's damaged from trying to be eaten. the hillstream loach isn't really a suitable tank mate for goldfish, they require different conditions ideally to keep them happy. The fin nippers if the goldfish are fantails are just a complete no no, the fins will just be far to tempting for them. Shrimp i wouldn't imagine lasting to long in the tank tbh either, goldfish may well be slow slower but trust me they will catch shrimp and will devour very easily.

I cant comment on the other fish suggested becasue i don't know anything about them.

I also and this is just personal think that a 2 foot cube tank isn't big enough for goldfish, the 220 litres is fine but a tank with more 'length' will be far more ideal than a tank that just has the volume of water.

Yep, completely agree with all of that, I wasn't disputing what you said in the first place.
All I was saying is that there are always more options.
The danios and tetras, as I said, weren't on my list of priorities, but I thought I'd include them just to show how small the list of suitable tank mates was, and what to avoid.
As I said with the hillstream loach, needs fast flowing water, you could replicate with power heads, and it will be easier in the cube tank as you won't have the power head aimed all the way along the tank, just a section.
The corys should be perfectly fine as they can reach 3", way too big for even a fully grown G-fish to eat.

I've always found that with G-fish, if they can't fit it in their mouth, they generally leave it alone. Of course this is personal experience and should be taken with a pinch of salt.
I've also found that if the fish are introduced when small, they don't have a problem with them, exactly the same as Angels with neons.

Only problem with the method you have is that is not a ideal situation to have, yes adding them both when small could lead them to be quite happy together but it's not really a forgone conclusion. If they did decide to see them as food (which is a huge possibility when the goldfish are much larger) then you don't have a choice but have missing fish which is potentially more heartache than it's worth.

Peppered cory's wont get to 3 inch, they usually don't reach 2 inches with alot actually staying a tad smaller than that which really does put them within eating range. Any other cory that i can think off my head wouldn't be suitable in ideal goldfish conditions (simply becasue of waste sitting at the bottom of the tank and temperature they ideally need).

Basically when i said there are only two options, i really don't think there's many more, you could possibly get things like weather lo aches if the tank is suitable but for any and most 'tropical' species the tank just isn't going to be suitable.

The hillstream loach doesn't really need the water that fast flowing tbh, very aerated and pristine water is more important but that could be a potential problem with goldfish in the tank.

If you have goldfish and you want to keep them, upgrade the tank and keep it coldwater with coldwater species only, goldfish really do produce stupid amounts of waste and even fancy goldfish can surpass 10 inches, leading to why i said the 2 foot cube tank isn't really a suitable option IMO.

 

[VaegaVic]

Only problem with the method you have is that is not a ideal situation to have, yes adding them both when small could lead them to be quite happy together but it's not really a forgone conclusion. If they did decide to see them as food (which is a huge possibility when the goldfish are much larger) then you don't have a choice but have missing fish which is potentially more heartache than it's worth.
True, heartache is never desired, but atleast it spices up a plain old tank with 2 fantails in it.

Peppered cory's wont get to 3 inch, they usually don't reach 2 inches with alot actually staying a tad smaller than that which really does put them within eating range. Any other cory that i can think off my head wouldn't be suitable in ideal goldfish conditions (simply becasue of waste sitting at the bottom of the tank and temperature they ideally need).
I happen to have 9, 2.5" peppered corys in my tank currently. The waste would be taken care of by frequent water changes using a gravel siphon, which is an absolute must with any goldfish. The reason I suggested Pep corys is because of their larger size and preferation for cooler water, with room temp being around 20C, pep cors love 15-25, so 20 is bang smack right in the middle. Sand in the tank will be perfect for spotting waste and for the corys.

Basically when i said there are only two options, i really don't think there's many more, you could possibly get things like weather loaches if the tank is suitable but for any and most 'tropical' species the tank just isn't going to be suitable.
I would never suggest weater loaches as they can very easily damage G-fish by ramming them or flicking them, usually resulting in the death of the fish from internal injuries. The same goes with tropical species, which is why I suggested Temperate.

The hillstream loach doesn't really need the water that fast flowing tbh, very aerated and pristine water is more important but that could be a potential problem with goldfish in the tank.
As far as I'm aware, aeration is very important for g.fish as they are larger and require more oxygen. The same goes with water quality. Problems with swimbladders due to aeration generally only occur when eating from the surface, not oxygen in the water.


If you have goldfish and you want to keep them, upgrade the tank and keep it coldwater with coldwater species only, goldfish really do produce stupid amounts of waste and even fancy goldfish can surpass 10 inches, leading to why i said the 2 foot cube tank isn't really a suitable option IMO.

Well as long as we're going by average sizes, most fantails don't reach their full size, most barely get over 16cm, which is 6 inches roughly. True they do spew masses of waste, but as I said earlier, this should be easily be taken care of by regular maintenance.
The other problem is that there are so very few coldwater species to chose from, which is why I suggested things like pep corys as they are temperate and can go in both coldwater and tropical.

The very fact that she is willing to spend the money on only 2 fish really shows commitment, anything is better at this point than the 25L tank.
If she has the money, the bigger the better, but at the same time, I'd always leave a little reserve for the unknown.
A bigger tank footprint would also be ideal when dealing with goldfish as this allows for more oxygen in the water. G.fish never grow to the size of the tank, but they can become stunted.

 

[greengoddess]

Wow, thank you all for this huge amount of advice. It is a bit overwhelming.

First of all, although my ID is greengoddess, I am of the male variety... just thought I'd clear that one up!

OK, let me also put down some firm markers that are unchangeable:


1. The two fish we have are definitely fancy goldfish (fantails).

2. I would almost certainly like to keep the tank as a coldwater tank so the additional fish stock would need to be very comfortable in typical coldwater conditions (20 celcius approx in my home).

3. I am a complete beginner so I don't want anything that would be difficult to maintain as I lead a very busy life.

4. This is going to be a one tank only affair. I definitely don't have the time for more than one tank as one would end up being neglected.



Also, if I do decide to buy the 220 litre cube, how long (realistically) do you think I would have before I would NEED to upgrade it to a larger one (assuming that the fish stock consisted of 2 fantails and a small number of the fish that you have kindly suggested?

 

[waterdrop]

Hi there male greengoddess

I would like to throw in some comments relative to your third firm marker:
(ie. easy maintenance)

I have very mixed feelings about the 220L cube you found when looking for the new big tank for the goldfish. First of all the cube shape part is actually ok in my opinion, a situation with goldfish, especially fancys, is better with cube tanks than any number of other types of fish would be. The major problem though is that you will find a tank that tall to be a huge headache for maintenance. All sorts of weekly jobs will be made much harder by the depth. In a tank one often needs to work at the substrate surface and in a tank like that you will find yourself buying all sorts of long extension devices and struggling with them.

A good rule of thumb that might help you would be to find the back of a chair or something and reach your arm over the edge, pretending you are sticking your arm down such that the water just goes a short bit above your moderately bent elbow - then measure the distance from the imaginary water line down to your fingers. In my case I find that about 17 inches of water depth is about all I'd like to deal with. That allows me to still work with things at the bottom surface with my fingers. I'm not saying it can't be done, with determination, just trying to tip you off to something you might not normally think of beforehand.

Another aspect of a tall tank is that although at first glance it seems to handily solve the problem of fish needing a bigger volume of water than one has, its really not solving it in the best way for the fish. One of the main reasons we seek larger volume for fish is actually to acheive larger surface area for greater gas exchange (oxygen coming in, CO2 going out, which happens with surface -movement-.) Technically (from a fish water chemistry perspective), a tall tank is actually a smaller tank than its volume indicates.

Secondly, a tall volume doesn't achieve the other main reason we seek higher volume for fish, which is horizontal swimming runs. As one can imagine, they just need to "stretch out their fins" sometimes as one can imagine. They are animals, not all that different from us, and need exercise to be healthy, so the bigger they are the more room needed for that. Still, I appreciate that these two particular goldfish have been saved from a slow death in a tiny volume and that you are already making things much better for them, so keep up the good work, just trying to give you information that might be helpful in the back of your mind! 220L, by the way, should be more than enough for two fancys and a couple of extra cold water minnows or whatever, its just the shape...

~~waterdrop~~

 

[greengoddess]

Hi there male greengoddess

I would like to throw in some comments relative to your third firm marker:
(ie. easy maintenance)

I have very mixed feelings about the 220L cube you found when looking for the new big tank for the goldfish. First of all the cube shape part is actually ok in my opinion, a situation with goldfish, especially fancys, is better with cube tanks than any number of other types of fish would be. The major problem though is that you will find a tank that tall to be a huge headache for maintenance. All sorts of weekly jobs will be made much harder by the depth. In a tank one often needs to work at the substrate surface and in a tank like that you will find yourself buying all sorts of long extension devices and struggling with them.

A good rule of thumb that might help you would be to find the back of a chair or something and reach your arm over the edge, pretending you are sticking your arm down such that the water just goes a short bit above your moderately bent elbow - then measure the distance from the imaginary water line down to your fingers. In my case I find that about 17 inches of water depth is about all I'd like to deal with. That allows me to still work with things at the bottom surface with my fingers. I'm not saying it can't be done, with determination, just trying to tip you off to something you might not normally think of beforehand.

Another aspect of a tall tank is that although at first glance it seems to handily solve the problem of fish needing a bigger volume of water than one has, its really not solving it in the best way for the fish. One of the main reasons we seek larger volume for fish is actually to acheive larger surface area for greater gas exchange (oxygen coming in, CO2 going out, which happens with surface -movement-.) Technically (from a fish water chemistry perspective), a tall tank is actually a smaller tank than its volume indicates.

Secondly, a tall volume doesn't achieve the other main reason we seek higher volume for fish, which is horizontal swimming runs. As one can imagine, they just need to "stretch out their fins" sometimes as one can imagine. They are animals, not all that different from us, and need exercise to be healthy, so the bigger they are the more room needed for that. Still, I appreciate that these two particular goldfish have been saved from a slow death in a tiny volume and that you are already making things much better for them, so keep up the good work, just trying to give you information that might be helpful in the back of your mind! 220L, by the way, should be more than enough for two fancys and a couple of extra cold water minnows or whatever, its just the shape...

~~waterdrop~~

Hi, your point about the depth of water and maintenance with the cube tank is something I had never even thought of! Thank you so much for pointing that out. This such a struggle to sort out. I really need the tank in my living room which would probably mean getting the cube. The only way I could get a large rectangular tank in my living room is by buying a flatscreen TV at the same time. I could get rid of my big box TV and then have room for a large rectangular tank. The new flatscreen TV would then be wall mounted. That is a possibility but then we're talking even more cash. I suppose I'm just going to have to make my mind up.

 

[JenCliBee]

VaegaVic, i hope you haven't took offence to my opinions. Seems to have gotten you a little riled up and that was far from my intentions .

Will comment back to your answers and please don't think in anyways im getting at you.

True, heartache is never desired, but at least it spices up a plain old tank with 2 fantails in it.

Unfortunately this is pretty much the consequences of having cold water fish with a tank, me personally think goldfish of any sorts should be kept in ponds but again this is my opinion.

I happen to have 9, 2.5" peppered Cory's in my tank currently. The waste would be taken care of by frequent water changes using a gravel siphon, which is an absolute must with any goldfish. The reason I suggested Pep corys is because of their larger size and preferation for cooler water, with room temp being around 20C, pep cors love 15-25, so 20 is bang smack right in the middle. Sand in the tank will be perfect for spotting waste and for the corys.

You may well have peppered cory's that big and i never said that you didn't, infact i never said they couldn't get that size but merely the usually don't. If you post in the cory section with average sizes to peppered cory's you will be given the same answer as ive mentioned previously. Peppered are actually considered one of the smaller species of cory and not one of the larger.

Ive seen peppered in shops huge but labeled under the name of 'jumbo' peppered cory's, weather this is man made or an actual species i don't know but the common peppered cory is considered small and really wont usually bypass 2 inches from my experience. I would love to see a picture of yours with some semblance of actual size compared to a tape measure for instance .

Basically when i said there are only two options, i really don't think there's many more, you could possibly get things like weather loaches if the tank is suitable but for any and most 'tropical' species the tank just isn't going to be suitable.
I would never suggest weather loaches as they can very easily damage G-fish by ramming them or flicking them, usually resulting in the death of the fish from internal injuries. The same goes with tropical species, which is why I suggested Temperate.

I never suggested the fish would be suitable, i said if the tank is suitable, i mentioned weather loach simply becasue i know of them been a cold water fish, i wouldn't have put what i did in bold above if i ment it was a definite choice that could go in , no matter what!!

The hillstream loach doesn't really need the water that fast flowing tbh, very aerated and pristine water is more important but that could be a potential problem with goldfish in the tank.
As far as I'm aware, aeration is very important for g.fish as they are larger and require more oxygen. The same goes with water quality. Problems with swim bladders due to aeration generally only occur when eating from the surface, not oxygen in the water.

This section actually confused me a little, i also like you said aeration is very important along with pristine water conditions not only for hillstreams but goldfish alike. Yes water quality is important to fish in general but maintaining that with such big messy fish may cause problems in the future. Not sure where the swim bladder part came from becasue i never mentioned that so wont comment any further becasue it isn't anything to do with the thread in question.

Well as long as we're going by average sizes, most fantails don't reach their full size, most barely get over 16cm, which is 6 inches roughly. True they do spew masses of waste, but as I said earlier, this should be easily be taken care of by regular maintenance.
The other problem is that there are so very few coldwater species to chose from, which is why I suggested things like pep corys as they are temperate and can go in both coldwater and tropical.

Ill have to disagree with you here, fantails within ponds often bypass 6 inches and do by a great margin. Yes you could say that within a tank environment they wont, but that is just invalid becasue in that case there is obvious reasons why it wont grow so big. Often than not it will be conditions of either a tank to small or conditions not been optimal which in both cases aren't an acceptable way to say they will grow this big and often don't get bigger when obviously they should and do in a different scenario like a pond.

I agree with the good maintenance regime, however what is a good maintenance regime to you?, would 20% weekly be sufficient or do you consider 50% sufficient?. In the light of goldfish and such big messy fish, daily cleaning of the waste would be ideal. Some people just wont keep to this regime or don't physically have the time to keep to this. Then not only do you have big messy fish to maintain the tank with, you have added bio load from various other little fish on top which make it even more important to keep to a high maintenance regime.

From my experience with any goldfish species is that they don't stop with the mess, the produce nearly all day everyday and that entails waste sitting around daily or for days until the next scheduled water change/gravel vac etc is done, this isn't going to be suitable for bottom dwelling fish like cory's long term and potential problems could arise which 'could' lead to not only the cory's becoming sick/ill but basically contaminating the whole tank including the beloved goldfish which seems to me is the main purpose of going to these lengths to keep them happy and safe from disease.

Again none of this is ment to be harsh or contradictive to your own beliefs or experience but one persons experience could be completely different to the next 100 people that have kept goldfish of any sorts.

 

[Curiosity101]

To be honest I think the cube should be fine for the fantails for 2 reasons:

1. Fancys aren't as fast as commons. So the fact that it is square shouldn't be a problem as they'll happily go up and down aswell as backwards and forwards.

2. Goldfish aren't really very good with plants anyways. So a good goldfish tank will probably have a couple of bits of driftwood, a couple of fake plants and some rock (or similar). And the only time you should need to touch the substrate is for vaccing. But if you buy a super long vac (or one of the extendable ones) then that shouldn't be an issue. Also you can get some pretty long algae scrapers.
The only think you need to think is that if it's in an alcove, do you have access from all three sides, because if you're just going into from the front it could still be a bit of a stretch.