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Mcfly1981

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Hello guys I’m Martyn. Im relatively new to owning tropical fish but I just wondered if the consensus of doing a 25% water change in my 80 Ltr tropical tank is bad for my fish? My other half seems to think that is too often although I reckon just about near to or just over my fish capacity... what do you guys and girls think?
 

Byron

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Welcome to TFF. :hi:

I'll respond in general since you have not indicated the tank size and fish load, filter, etc, etc. So assuming a biologically balanced aquarium, you should do one water change every week (on the same day of each week, it is easier to get into a habit like this) and it should be substantial. This means at the very least a 50% change but preferably 60-70%. I have been doing 65-75% water changes weekly for well over a decade now on several tanks in my fish room.

The point with water changes is to maintain stability. Substances accumulate in the water, stuff that cannot be dealt with by any filter or filtration (aside from flow-through water which few if any aquarists have) and the only way to remove these things is with a good water change. Provided the parameters (being the GH, pH and temperature) are reasonably similar, you really cannot change too much water. :fish:
 

Naughts

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"Over-cleaning" would be to cause a tank to lose all or most of its beneficial bacteria, maybe by scrubbing all surfaces and decor and cleaning the filter and gravel with tap water all at once. The tank would then need to recycle.
Beneficial bacteria are on surfaces, not in the water column, so lots of high volume water changes are not detrimental at all. As you said, if your tank is heavily stocked it's even more important to change a lot of water to deal with the pollution.
 

Lilyann

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In my discus tank, which has adult discus, I do 2 x 50-75% water changes weekly.
In my shrimp tanks with micro-fish species I do 25% water changes weekly.
In my 30 gallon, which has a group of 6 very small, juvenile Praecox rainbow-fish I do around 25-30 % weekly. It is also very heavily planted.
In my 180 gallon I do 1 50-75% weekly.
All my tanks are also moderately- heavily planted. This also will make a difference in the amount of water required to be changed weekly.

As you can see- It depends. Discus, of course, require more frequent and higher volume changes, nano-fish/shrimp require less.
But, in my experience, all fish benefit from a weekly water change-- the amount and frequency needs context.
 

Deanasue

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Always do a 75% water change when I clean on Mondays and another 50% on Thursdays. In an established tank your cycle won’t be affected.
 
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Mcfly1981

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Thanks for that I guess I’m under cleaning basically then.... I have an 80ltr tank with an EHEIM 120 filter. My stock is as follows.

4x black skirt tetra
5x Neon
2x gold Platy
2x ottos
2x Hill stream loach
1x mollie
1x pearl Gourami
1x armoured Shrimp
 

Deanasue

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Thanks for that I guess I’m under cleaning basically then.... I have an 80ltr tank with an EHEIM 120 filter. My stock is as follows.

4x black skirt tetra
5x Neon
2x gold Platy
2x ottos
2x Hill stream loach
1x mollie
1x pearl Gourami
1x armoured Shrimp
Everyone should do a 75% water change and cleaning once a week, IMO. I do the 2nd one because I have 2 tanks of goldfish that have heavy bio loads and one other community tank that is a little overstocked. I actually change my bettas every 2 days because they have long tails and fins.
 

Colin_T

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In my 30 gallon, which has a group of 6 very small, juvenile Praecox rainbow-fish I do around 25-30 % weekly. It is also very heavily planted.
You want to do bigger water changes for rainbowfish because they are prone to developing protozoan infections like Costia, Chilodonella and Trichodina if kept in dirty water.

I did 75-90% water changes and complete gravel cleans every week, on all my tanks.
Just make sure any new water is free of chlorine/ chloramine before it's added to the tank.

--------------------------
You do water changes for 2 main reasons.
1) to reduce nutrients like ammonia, nitrite & nitrate.
2) to dilute disease organisms in the water.

Fish live in a soup of microscopic organisms including bacteria, fungus, viruses, protozoans, worms, flukes and various other things that make your skin crawl. Doing a big water change and gravel cleaning the substrate on a regular basis will dilute these organisms and reduce their numbers in the water, thus making it a safer and healthier environment for the fish.

If you do a 25% water change each week you leave behind 75% of the bad stuff in the water.
If you do a 50% water change each week you leave behind 50% of the bad stuff in the water.
If you do a 75% water change each week you leave behind 25% of the bad stuff in the water.

Fish live in their own waste. Their tank and filter is full of fish poop. The water they breath is filtered through fish poop. Cleaning filters, gravel and doing big regular water changes, removes a lot of this poop and makes the environment cleaner and healthier for the fish.
 
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Mcfly1981

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Cheers,
thanks guys I will be more attentive to my fish from now on....!
 

seangee

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Do you know the hardness of your water. You have some fish that need very hard water and others that need very soft. I'm afraid it will not be possible for these to thrive in the same water. We need to know the actual number as well as the unit.

Your fish also have very different requirements for current. Again you have species that require both extremes. I have not checked on temp requirements but you should check the species profile on seriouslyfish.com to establish what will work together in your tank.
If you post your hardness figures others can advise as a starting point
 

Lilyann

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You want to do bigger water changes for rainbowfish because they are prone to developing protozoan infections like Costia, Chilodonella and Trichodina if kept in dirty water.

I did 75-90% water changes and complete gravel cleans every week, on all my tanks.
Just make sure any new water is free of chlorine/ chloramine before it's added to the tank.

--------------------------
You do water changes for 2 main reasons.
1) to reduce nutrients like ammonia, nitrite & nitrate.
2) to dilute disease organisms in the water.

Fish live in a soup of microscopic organisms including bacteria, fungus, viruses, protozoans, worms, flukes and various other things that make your skin crawl. Doing a big water change and gravel cleaning the substrate on a regular basis will dilute these organisms and reduce their numbers in the water, thus making it a safer and healthier environment for the fish.

If you do a 25% water change each week you leave behind 75% of the bad stuff in the water.
If you do a 50% water change each week you leave behind 50% of the bad stuff in the water.
If you do a 75% water change each week you leave behind 25% of the bad stuff in the water.

Fish live in their own waste. Their tank and filter is full of fish poop. The water they breath is filtered through fish poop. Cleaning filters, gravel and doing big regular water changes, removes a lot of this poop and makes the environment cleaner and healthier for the fish.
Thanks Colin-- Ive been keeping fish for 3 decades. Some of the most sensitive, wild species out there available to hobbyists. I know why fish need water changes ( I realize it is more than nitrates we are speaking of here) and I disagree with the necessity for one size fits all assessment of weekly water changes-- huge ones every week. There are many factors and scenarios that would mitigate that necessity: plants, uv sterilizers, density of live-stock, to name a few.

I am aware of bio-load and bacterial load. Thats why two of my tanks that are heavily stocked have top-shelf UV systems.

But, my 6 juvenile fish in my 30 gallon- who happen to be f4 Gary Lange stock- the amount and frequency is more than adequate. Lets be reasonable here- we need to think contextually and not just repeat a general "one-size fits all" rule to fish in the aquarium. .
-
 

Byron

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Do you know the hardness of your water. You have some fish that need very hard water and others that need very soft. I'm afraid it will not be possible for these to thrive in the same water. We need to know the actual number as well as the unit.

Your fish also have very different requirements for current. Again you have species that require both extremes. I have not checked on temp requirements but you should check the species profile on seriouslyfish.com to establish what will work together in your tank.
If you post your hardness figures others can advise as a starting point
These are both extremely important issues here, and need to be resolved so that the health of the fish will be good.
 

Byron

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Thanks Colin-- Ive been keeping fish for 3 decades. Some of the most sensitive, wild species out there available to hobbyists. I know why fish need water changes ( I realize it is more than nitrates we are speaking of here) and I disagree with the necessity for one size fits all assessment of weekly water changes-- huge ones every week. There are many factors and scenarios that would mitigate that necessity: plants, uv sterilizers, density of live-stock, to name a few.

I am aware of bio-load and bacterial load. Thats why two of my tanks that are heavily stocked have top-shelf UV systems.

But, my 6 juvenile fish in my 30 gallon- who happen to be f4 Gary Lange stock- the amount and frequency is more than adequate. Lets be reasonable here- we need to think contextually and not just repeat a general "one-size fits all" rule to fish in the aquarium. .
-
I am not trying to be argumentative here, but there is some misunderstanding. It is certainly true that live plants, stocking density, etc will impact or have consequences or be variable factors on the biological system, but none of these can replace water changes.

Fish in their natural habitat are in "fresh" water with every respiration of their gills. This is not even remotely possible in an aquarium unless you have flow-through water which I doubt anyone on this forum has.

Live plants benefit, no doubt of that. But I recall one assessment that if you had six black neon tetras in a 55 gallon well planted aquarium, you would have the ratio of plants/fish that would negate water changes. Plants cannot compensate for lack of water changes.

UV is actually not beneficial in a freshwater system. For one thing, unless every drop of water in the aquarium passes through the UV before it returns to the aquarium--i.e., you would need the UV between two tanks with water passing from one through the UV to another--it is not going to do much. And this still does not replenish the water as "fresh" but merely makes it less beneficial in a sense.

There are substances accumulating in the water from fish that cannot be removed except by a water change. Fish release pheromones that others in the species read, and allomones that are read by other species. These accumulate quite densely in an aquarium, and they cause stress to fish when they are negative. The only way to remove them is with substantial frequent partial water changes.

The other point to keep in mind is that the more water you change the healthier the fish will be, always. Jack Wattley in his monthly discus column in TFH frequently mentioned water changes, and noted that some discus breeders change 95% of the water in the fry tanks two and even three times every day. This allows them to have more fry per tank, and the fry develop faster and are healthier. The point of my mentioning this is not to suggest overstocking tanks, but to illustrate the incredible benefit of water changes. Imagine providing these benefits to all one's fish? Less stressed fish means healthier fish, since stress is the direct cause of 95% of fish disease in an aquarium.

Fish do not become sick from clean water, only when it is not changed. And a 70% change once a week is far more beneficial than 10% changed every day, even though in the end the same "volume" has been changed over seven days. Regular substantial water changes are the most important and frankly crucial maintenance an aquarist can do for his fish.
 
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