Adding sand as substrate to established gravel tank

A Fishkeeper

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Hi,

I have an established tropical tank with gravel substrate. It’s looking a little tatty and in need of a new look. I was wondering about putting my gravel in mesh bags. Adding some sort of nutritious substrate for plants(in mesh bags also) and then putting a layer of sand for appearance and easier planting. I don’t want to lose all my beneficial bacteria that’s living in the gravel and think the gravel being under the sand will give depth and help keep costs down.

Is this a realistic idea?
In my head it works 😅
 
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Byron

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The gravel (inert presumably) in mesh bags will have no actual benefit. While it is certainly true that the substrate is the primary bacterial bed, replacing the substrate totally (which I have done many times over the years) does not cause serious issues. Provided it is done correctly, there may be anaerobic areas in the gravel (this is normal and useful to the biological system) and you don't want to disturb these with fish in the tank, but changing the substrate on its own is not problematic.

As for some sort of plant substrate, another member reported on this but here again the benefit is limited if it even exists. Plants will grow very well in inert sand, I've done if for over 30 years (gravel initially, changed to sand about 10 years ago), and substrate tabs are easy to use for larger plants that would benefit. [edit, addion:] Most plant substrates can detrimentally impact fish, so this is another reason not to use them.

Sand is in most cases a better substrate, no issues for plants and some fish (like Corydoras) need sand. Just move the fish to a temporary tank so you are not rushed, and this is far less stressful on fish that trying to do a change with the fish present.
 
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Guyb93

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Have a look at MD on YouTube he uses the mesh bag idea works well for banking up substrate or reusing aqua soil
 

Wills

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What Byron has said is all great advice but I'm guessing you've seen some of the aquascapers doing this kind of thing.

I would add the gravel and an aquarium soil to the bags and build them up under the sand, the advantages are that you get the planted substrate in there, which in this purpose is the same as using root tabs which a lot of people that just use sand do anyway. You also get the deeper slope to add visual depth to the tank without banking the sand really high and the risks with that plus deep sand alone will just level out over time.

When you do it just monitor your tests though and respond accordingly.

Wills
 
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The gravel (inert presumably) in mesh bags will have no actual benefit. While it is certainly true that the substrate is the primary bacterial bed, replacing the substrate totally (which I have done many times over the years) does not cause serious issues. Provided it is done correctly, there may be anaerobic areas in the gravel (this is normal and useful to the biological system) and you don't want to disturb these with fish in the tank, but changing the substrate on its own is not problematic.

As for some sort of plant substrate, another member reported on this but here again the benefit is limited if it even exists. Plants will grow very well in inert sand, I've done if for over 30 years (gravel initially, changed to sand about 10 years ago), and substrate tabs are easy to use for larger plants that would benefit. [edit, addion:] Most plant substrates can detrimentally impact fish, so this is another reason not to use them.

Sand is in most cases a better substrate, no issues for plants and some fish (like Corydoras) need sand. Just move the fish to a temporary tank so you are not rushed, and this is far less stressful on fish that trying to do a change with the fish present.
Thanks for all the knowledge you’ve just shared. I have a bristlenose, 3 neon tetras, 4 black mollies and a large number of assassin snails. It’s a 75 litre tank but I don’t have another tank to put them in. I have buckets I can put them in clean buckets for a very short time but wouldn’t have a filter in it but I could put heater and bubble stone.
Any thoughts/advice?
Thanks
 
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Have a look at MD on YouTube he uses the mesh bag idea works well for banking up substrate or reusing aqua soil
yes, this is where I got the idea from. Thought it made a lot of sense. I’m just scared of killing my fish by not doing it properly. I only saw him doing to a new aquarium not adjusting an already established one which is the scary bit 😰
 
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What Byron has said is all great advice but I'm guessing you've seen some of the aquascapers doing this kind of thing.

I would add the gravel and an aquarium soil to the bags and build them up under the sand, the advantages are that you get the planted substrate in there, which in this purpose is the same as using root tabs which a lot of people that just use sand do anyway. You also get the deeper slope to add visual depth to the tank without banking the sand really high and the risks with that plus deep sand alone will just level out over time.

When you do it just monitor your tests though and respond accordingly.

Wills
Thanks for advice. Yes, the depth is what I was hoping for and I find plants either thrive or die in this tank. My larger tank seems to do much better with plant variety and without daily liquid fertiliser but this tank needs daily(5 days out of 7) dosing for plants to live. So as well as changing the subtracts for the aesthetics I want to do it for the plants so I can have variety.
 

Byron

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Thanks for all the knowledge you’ve just shared. I have a bristlenose, 3 neon tetras, 4 black mollies and a large number of assassin snails. It’s a 75 litre tank but I don’t have another tank to put them in. I have buckets I can put them in clean buckets for a very short time but wouldn’t have a filter in it but I could put heater and bubble stone.
Any thoughts/advice?
Thanks

When I changed over one of my tanks, i used a spare 20g. You could pick up one of these, or a 15g long. Some people use one of those "plastic" boxes (can't remember the name!). Provided you can put the heater and filter in this temporary "tank" you're fine. Things can occur along the way, and with the fish in an environment where they can stay for a day or two or three, no worries. I would not use common buckets. You want some of the decor from the tank in the temp so the fish have security. And plants can be laid on the surface.

On another matter...mollies attain 4-5 inches (or should if healthy) so you need to re-think them, this tank is too small, and they have a significant bioload impact, since they are heavily vegetarian. The neons should be in a group of 10 (or more).
 
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Just a regular plastic box that I can buy from a supermarket or something more fish specific? (Obviously rinsed first)
 

Wills

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The way MD does it is all recycling from old tanks, he uses a sand, soil, gravel mix thats full of roots and root tabs and its all beneficial its just not going in the same tank.
 
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When I changed over one of my tanks, i used a spare 20g. You could pick up one of these, or a 15g long. Some people use one of those "plastic" boxes (can't remember the name!). Provided you can put the heater and filter in this temporary "tank" you're fine. Things can occur along the way, and with the fish in an environment where they can stay for a day or two or three, no worries. I would not use common buckets. You want some of the decor from the tank in the temp so the fish have security. And plants can be laid on the surface.

On another matter...mollies attain 4-5 inches (or should if healthy) so you need to re-think them, this tank is too small, and they have a significant bioload impact, since they are heavily vegetarian. The neons should be in a group of 10 (or more).
Sorry, just read the second part of your reply. I had 6 neons as was told that would make them happy and not be too many but they have slowly died one by one. The mollies are the reason I got the second smaller tank (the biggest I could fit in my living room and afford), i made the mistake of buying male and female mollies when I first got my bigger tank 2 years ago. They had loads and loads of babies I couldn’t get rid of them because local fish store stopped taking fish from people. So I decided to separate males and females. It’s by no means ideal I started with 6 males together but they have slowly got poorly and died but I don’t have any alternative. Only 2 of the males grew to full size and one of those suddenly died a couple of weeks ago. The other have all stayed a lot smaller but still feisty. No one wanted them and they have survived over a year together mostly healthy. My 3 females in the bigger tank are all full size.

Sadly I have made many mistakes in learning to keep fish happy and healthy but I’ve tried my best and I will just not make the mistake of buying male and female live bearers again 🤯😱
 

Byron

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Just a regular plastic box that I can buy from a supermarket or something more fish specific? (Obviously rinsed first)

It has to be large enough. I used these when I moved. They have a lid which is handy in moving (no lost fish from jumping out). Get very heavy with water though. But one that holds 15 or 20 gallons might work quite well.
 
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It has to be large enough. I used these when I moved. They have a lid which is handy in moving (no lost fish from jumping out). Get very heavy with water though. But one that holds 15 or 20 gallons might work quite well.
Brilliant, thank you. I will do it that way, thank you. Will keep it so I can use it another time if needed.
 

Byron

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Sorry, just read the second part of your reply. I had 6 neons as was told that would make them happy and not be too many but they have slowly died one by one. The mollies are the reason I got the second smaller tank (the biggest I could fit in my living room and afford), i made the mistake of buying male and female mollies when I first got my bigger tank 2 years ago. They had loads and loads of babies I couldn’t get rid of them because local fish store stopped taking fish from people. So I decided to separate males and females. It’s by no means ideal I started with 6 males together but they have slowly got poorly and died but I don’t have any alternative. Only 2 of the males grew to full size and one of those suddenly died a couple of weeks ago. The other have all stayed a lot smaller but still feisty. No one wanted them and they have survived over a year together mostly healthy. My 3 females in the bigger tank are all full size.

Sadly I have made many mistakes in learning to keep fish happy and healthy but I’ve tried my best and I will just not make the mistake of buying male and female live bearers again 🤯😱


We have all been down the road of mistakes. If one learns from them, that at least is something.

You are in London UK, with (I believe) very hard water. This is fine for livebearers (mollies should do well, water-wise) and some other fish, but not so good for neon tetras or most tetras unfortunately. May have been part of the loss, along with poor quality neons these days.
 
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We have all been down the road of mistakes. If one learns from them, that at least is something.

You are in London UK, with (I believe) very hard water. This is fine for livebearers (mollies should do well, water-wise) and some other fish, but not so good for neon tetras or most tetras unfortunately. May have been part of the loss, along with poor quality neons these days.
Yes I’m in London. Very hard water. I got them from pets at home and I think they have some underlying problem because a couple have bent spines now but it doesn’t seem to effect them. I’m not replacing any of the fish that die because it’s not what I would choose but I could at least make the take look prettier and try and give the best life to these fish I am able to. My assassins snails love this tank and breed like rabbits. Wish I could sell some. I paid £15 for 5 snails I now have over 50(that’s a total guess, some are teeny)
 

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