Water changes - how much is too much?

[IHaveADogToo]

The overachiever in me tends to do water changes of around 10%-20% every 2-3 days, and a big water change (30%+) bi-weekly. I just like keeping the water clear, and keeping the substrate free of debris, waste, and leftover food. And, clean water is always good for fish. When I only had one tank, I was doing water changes once a week. But now that I have several tanks, I'm doing it every couple days. To me, it just seems like doing a small water change and gravel vac every couple of days helps keep any toxins diluted, and it's just easier to do more frequent, small water changes, than it is to do a big water change every week.

Of course, my friends who don't keep fish are suddenly experts, and say I'm changing the water too often.

Is there such a thing? Is it really possible to do too many water changes? Sure, I could understand the commotion of all that activity being stressful on some fish, but I don't believe fish can have too much clean water. And I'm only doing large water changes, of more than 30%, every other week. Besides, at this point, my fish are already familiar with the water change process and don't appear to be phased by it, if anything, they are curious about the hose, and I have to be careful because they try to swim into it.

Yes, when I change my water I am treating the new water with dechlorinator and bacteria product. Occasionally a light amount of aquarium salt if something looks wrong (less than half the recommended dose).

Most of my fish have come from pet stores like PetSmart, and their condition has only improved since I got them. I'm convinced it's because they are always getting clean water, which IMO is the best remedy for keeping fish healthy. But, like I said, my friends who don't keep fish are suddenly experts and are convinced I'm going to kill my fish by changing their water too frequently.

So, what do you think? Is there such a thing as too many water changes?

 

[Demeter32]

The point of water changes is to remove nitrates and fish chemicals (such as growth inhibiting chemicals from fry) as well as replenish minerals that the fish/plants need. You can never do too many water changes IMO. Breeders do large daily water changes or even twice daily water changes upwards of 50% and it doesn't harm the fish. Of course how often and how much you change the water depends on the size and stocking of the tank as well as how quickly nitrates build up and minerals are used.

I always do 50% water changes but usually just once a week unless it is a fry tank, in which case I will do 2-3 50% water changes a week.

Newbie fish keepers or un-informed people (not all but some) assume all you need to do is feed the fish and replace evaporated water. When they think of cleaning a tank they mean completely drain, remove the fish, and scrub the entire tank down. Don't bother listening to your friends, they know nothing. Even my family comments on how often and how much I change the water. I don't usually reply because do not tell me how to care for my fish, I did my research and know what I'm doing.

 

[IHaveADogToo]

do not tell me how to care for my fish.

This is the best advice right here... thanks for that.

 

[fluttermoth]

Larger water changes are more effective than smaller ones, as they dilute everything more. IMHO, you're not changing enough water. I'd much, much rather do one really good water change (and, again IMHO, that's at least 50% a week) than faff around doing lots of small ones.

What level is the nitrate, both in the tap water and in your tank? Although reducing nitrate is not the only reason we do water changes, it is a good indicator.

 

[fluttermoth]

do not tell me how to look after my fish

This is the best advice right here... thanks for that.

I did my research and know what I'm doing.

No, this is the best advice!

 

[Byron]

We have had this discussion a few times on this forum, but there is certainly no problem having it more often because the importance of water changes need to be understood and kept in mind.

To answer your direct question, no, generally it is not possible to change too much water. The more water changes, the healthier the fish will be, this is a scientific fact. However, quantity is important, more so than frequency, again generally speaking. The more water you change at each water change, the better. And doing a larger change once a week minimum is more effective than smaller more frequent changes.

So first off, I would suggest you decide on a water change once a week, on the same day so set aside a day when you are normally not going to be sidelined by any other issues from week to week; I do mine on Sunday mornings, and it takes me three hours, a bit longer if I do any aquascaping. I have a fish room of eight tanks.

Second, change at least half the tank volume, preferably more. I change 60-65% generally, more maybe but never less. There is no problem doing this, provided the parameters between tank water and fresh water are reasonably similar. By parameters I mean GH, KH, pH and temperature. Larger changes do work to maintain more stability week to week. For example, nitrate should not increase from one water change to the next; if it does, then something is wrong. The goal of water changes is to maintain stability, so those who think they only need do a water change if nitrates rise or some other factor tests abnormal are going down the wrong road. However, some abnormality is often best addressed first by a significant water change and then looking for the issue.

The only time there should be a risk in doing a larger water change is when the biological system is out of balance. For example, if you go away for a week and someone else overfeeds the fish, you may come back to a tank that has increased ammonia, higher nitrates, lower pH. Doing a massive water change here could kill the fish from something like a sudden change from ammonium (in acidic water ammonia is the non-toxic ammonium form) to ammonia if the pH should suddenly rise above 7. But for a regular weekly change, you really cannot change too much water. If the tank is biologically balanced (fish load, volume, aquascape, fish feeding, plants, etc) a water change cannot be detrimental but certainly beneficial.

I always use the example of many discus breeders who change 95% of the water in their fry tanks once, twice, sometimes three times a day. You shouldn't need to be doing this, but it shows the value of fresh water. The fry grow faster and are much healthier. It also allows the breeder to keep more fry in a given tank, obviously. But that in itself shows the value of water changes on fish health and development.

Now to two items you mentioned that are somewhat troublesome. Bacterial supplement at a water change is not necessary, and while it may not be harmful there is no value in adding any substance to the water a fish then takes in and which enters the bloodstream and internal organs. Clean water with as few additives as necessary, no more.

Salt...should absolutely never be added to a tank holding freshwater fish species--except as a treatment for a specific disease/problem when salt is the best remedy. As some sort of "tonic" it is not only useless but detrimental because it gets inside the fish and does cause issues. I have a published article on salt that details the reason, and there are other articles by Neale Monks on the same subject at this site:
http://wetwebmedia.com/SaltArtHosking.htm

 

[IHaveADogToo]

Hey thanks for the replies!

It's interesting how my friends are telling me I'm doing too many water changes, and you all are telling me I could do more

@Byron and @fluttermoth, you guys are probably right in that I could be changing larger quantities. But, as for my habit of vacuuming the substrate every couple of days... yeah, don't expect me to break that habit any time soon. I like I tidy tank. Really, that's why I do the small, incremental changes. To keep the substrate clean, and to get any floating debris. But it's good to know that I probably should be doing a larger water change more often than I am. I will start doing that. I have no problem with it. Although, I think I need to buy more buckets.

I feel very validated by these replies.

 

[Byron]

@Byron and @fluttermoth, you guys are probably right in that I could be changing larger quantities. But, as for my habit of vacuuming the substrate every couple of days... yeah, don't expect me to break that habit any time soon. I like I tidy tank. Really, that's why I do the small, incremental changes. To keep the substrate clean, and to get any floating debris. But it's good to know that I probably should be doing a larger water change more often than I am. I will start doing that. I have no problem with it. Although, I think I need to buy more buckets.

There could be a problem with this over-cleaning of the substrate. You want organics to settle on and down into the substrate. The finer the substrate (meaning, sand as opposed to say pea gravel) the better because this encourages the bacterial decomposition that is essential to a healthy aquarium. The substrate is far more important than the filter; a host of various species of bacteria live in the substrate, many more species than in the filter. And while the filter is primarily intended as nitrification (bacteria or archaea) of ammonia to nitrite to nitrate, this is only the beginning of the story. Much more occurs in the substrate beyond these preliminaries.

Live plants help, as do the small snails that eat all organics (like fish excrement) and break it down faster. This is the single most important aspect of the aquarium, what goes on in the substrate.

To the issue of accumulations of detritus on the surface...I never see this unless the fish (like cories and loaches) stir up the sand during feeding. And as I have relatively small fish, it is not much to notice anyway. And a finer substrate does help, and a mix-tone sand. When I had black in one tank it was very obvious, though mostly larger things like bits of plant leaf and such.

 

[IHaveADogToo]

Salt...should absolutely never be added to a tank holding freshwater fish species--except as a treatment for a specific disease/problem when salt is the best remedy. As some sort of "tonic" it is not only useless but detrimental because it gets inside the fish and does cause issues. I have a published article on salt that details the reason, and there are other articles by Neale Monks on the same subject at this site:
http://wetwebmedia.com/SaltArtHosking.htm

Salt seems to be a heavily debated topic. Even here on this site. Some people swear by it, others avoid it like the plague. I only use it in rare cases, not frequently, so please don't misunderstand. It only gets used if someone has a ripped fin or something. And like I said, I use less than half the directed amount. When I do use it, I increase the quantity of water I change, as well, so I might do 30% water changes every couple of days instead of 10-20%, and then do a really big water change that week. When I use salt, I get concerned about leaving the salt in the tank too long, and just kind of instinctively kick-up my water change routine a few notches.

 

[Byron]

Salt seems to be a heavily debated topic. Even here on this site. Some people swear by it, others avoid it like the plague. I only use it in rare cases, not frequently, so please don't misunderstand. It only gets used if someone has a ripped fin or something. And like I said, I use less than half the directed amount. When I do use it, I increase the quantity of water I change, as well, so I might do 30% water changes every couple of days instead of 10-20%, and then do a really big water change that week. When I use salt, I get concerned about leaving the salt in the tank too long, and just kind of instinctively kick-up my water change routine a few notches.

If you read my article I linked, you will see that there is no benefit in what you describe here, none at all. The salt is not sufficient quantity to be beneficial (and torn fins wouldn't benefit anyway compared to clean water), but it does (guaranteed) impact the fish. Livebearers would be the least affected, but soft water species could have serious internal reactions.

 

[IHaveADogToo]

If you read my article I linked, you will see that there is no benefit in what you describe here, none at all. The salt is not sufficient quantity to be beneficial (and torn fins wouldn't benefit anyway compared to clean water), but it does (guaranteed) impact the fish. Livebearers would be the least affected, but soft water species could have serious internal reactions.

Yes I just heated up some lunch and I'm going to read it while I eat. Thankfully I already knew not to use it on a tank with scaleless fish, so I haven't dosed the community tank with it. I have only been using it on a betta who didn't get along with his last roommate. He's *is* healing, I can see him healing, so that's why I haven't asked for advice. But that could have more to do with me obsessively giving him fresh water than the salt dose.

 

[IHaveADogToo]

So basically, @Byron, what you're saying is this salt treatment is more of a placebo and might actually cause harm, and by obsessively vacuuming my substrate I'm creating a "bubble boy" environment?

 

[Colin_T]

It's interesting how my friends are telling me I'm doing too many water changes, and you all are telling me I could do more

not so much more water changes, just bigger ones

I did 50-75% water changes and complete gravel clean each week on most tanks. If the tanks are being fed heavily because I was conditioning fish for breeding, I did 80-90% water changes and complete gravel cleans. For marine tanks I simply drained them so there was enough water for the fish, then refilled them (90-95% water changes).

Rearing tanks got 10-20% for the first few weeks but when the fry were feeding properly they got 90% water changes and complete gravel cleans every day.

These water changes were all done with water that had been dechlorinated and aerated for several days to a week, and any new water going into a tank must be free of chlorine/ chloramine before it is added to the tank.

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It comes down to percentages. If you change 20% of the water you theoretically remove 20% of the ammonia, nitrite, nitrate, etc, and 20% of the harmful pathogens in the water.
Compare that to a 50% water change where you dilute everything by half.
And compare that to a 75% water change where you dilute everything by 75%.

The fish are healthier in water with fewer parasites and disease organisms so doing a bigger water change will remove more harmful substances and organisms in the water, making it cleaner for the fish.

A clean filter is also a must for healthy fish. Any filter with gunk in can add harmful pathogens to the water the fish live in.

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For everyone who doesn't like removing the gunk from the substrate, if you ever work in a fish shop, quarantine facility or aquaculture facility, you will quickly learn that clean gravel contributes to a clean tank. And tanks with a lot of gunk in the gravel will have more problems with fish dying from unexplained deaths. You will also have more trouble treating diseases in tanks because the medication gets wasted on the gunk and the organisms living in the gunk, instead of treating the actual fish. This is the main reason quarantine/ hospital tanks don't have gravel. The fewer objects that hold gunk, the fewer pathogens that will live in the gunk, and the better medications work.

Fish live in a soup of microscopic organisms and their own waste. How would you like to live in a sewerage tank, because that is pretty close to what a dirty fish tank with lots of gunk in the substrate is.

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If you are going to treat a fish, clean the glass, clean the filter, gravel clean the substrate and do a big water change to dilute the disease organisms in the water and filter. The bigger the water change, the more disease organisms you remove, leaving fewer pathogens behind to infect the fish. Then identify the disease correctly and use the appropriate medication at the recommended dose for the fish and disease.

If you want salt in the water for certain fishes like mollies, that is fine, but for fish that naturally occur in pure fresh water, salt can damage their kidneys if they are exposed to it for long periods. Salt (sodium chloride) is very useful at treating fungal and protozoan infections, but using low levels continuously will not benefit most freshwater fishes.

The dose rate for treating freshwater fishes with salt is 1 heaped tablespoon of salt per 20 litres of water. This can be doubled for severe protozoan infections but the fish should only remain in this salty water for 2 - 4 weeks. Two weeks is minimum to kill all the pathogens, and don't keep them in the salt water for more than 4 weeks because that can cause kidney damage.

If you keep wild caught discus, angelfish or Corydoras, then do not use salt unless you have no other options, and only use the lower dose rate of 1 heaped tablespoon per 20 litres.

 

[Ch4rlie]

I change my tank water every Sunday and usually around 50 - 60%. That’s including my nano shrimp tanks.

I change the filter floss in all filters that has floss during every water change as well, this helps keep the water nice and clean.

Rarely do I gravel vac the substrate, I just simply remove the worst of any debris or dead leaves from the surface. I do this because the leftover debris will simply turn into substrate mulm for the plants.

Once satisfied of water changes, I then add any catappa leaves and addition of plant ferts in each tank to keep everything tickety boo.

Pretty simple but works very effectively for me. Takes me around 1.5 to 2 hours to everything from start to finish. Does not feel that long when am doing this as I actually quite enjoy the process, am strange that way but that’s one of the enjoyments of the hobby, the satisfaction of a good water change routine and seeing all nice and clean for the fish

 

[IHaveADogToo]

n
It comes down to percentages. If you change 20% of the water you theoretically remove 20% of the ammonia, nitrite, nitrate, etc, and 20% of the harmful pathogens in the water.
Compare that to a 50% water change where you dilute everything by half.
And compare that to a 75% water change where you dilute everything by 75%.

I want to address this in particular, because here's my line of thinking... These percentages you are giving me are weekly numbers.

For example: If person A does a water change of 50% once a week, and person B does 20% water change 3 times a week, who will have cleaner water? That answer depends on the day. Sure, person A's water may be cleaner right after a water change, but it will be more toxic just before a water change. Person B's water will be more consistent, and may have a higher toxicity level just after a water change, but will have a lower toxicity level just before. We all agree that toxicity should be as close to 0 as possible, which is why I still have been doing bigger water changes biweekly.

This is just my thinking on this. If I'm way off base, someone correct me.