% Water Change Maximum?

[FunkSolid]

When you do a water change, what % do you change and why? Additionally do you believe there is a healthy limit on how much water can be exchanged at once without causing harm to aquarium and why? I know the obvious reality exists that you cannot remove 100% of the water with fish inside tank (lets just get that out of the way), but you could do a 90% water change, fill to 50% and then do another drain to 10% full and fill again. I know it sounds crazy and excessive but it makes a 90-99% water change plausible.

Thanks for your insight!

Andrew

[jvision]

Discus keepers will do 90% WCs several times per week. I know quite a few breeders who'll do at least 50% twice per week. The reason for all of that WC is to keep waste at a bare minimum; there's also evidence to suggest that larger juvies produce a growth-inhibiting hormone, so the WCs will help ALL of your baby fish have decent growth-rates. I do 50% WC/week because I kept planted tanks for years, using the Estimative Index method of fertilizing, which makes sure you have all required nutrients in excess for the plants - the 50% WC resets the tank each week so that unused nutrients don't overwhelm the tank after a while.

If you're doing REGULAR WCs, I don't think there is a max; however, if you're lazy and only change the water once in a while, it's best not to do huge changes. That could cause the fish to go through a shock; even though you're giving them a nice new, clean environment, the drastic change could be too much for them.

[geleen]

Agree with Jason.

Ideally I believe that having a flow through system of changing 100 percent, 1-3 times a day would be ideal for most kept species.

[syno321]

What J said. I do 90 % changes once or twice a week on overstocked raise-out tank. I would suggest fish from lakes, especially Tanganyka, do not tolerate massive water changes as well.

[Psylant]

Assuming that the water you're putting back into the tank is the right temperature and has been treated, I don't think there's a change "too large". I would agree with jvision about the filthy tank to 100% change type of scenario though with non-hardy inhabitants. The water chemistry would just be too different unless the change was done very slowly over the period of a few hours to allow for acclimation.

[firestorm]

I typically do anywhere from 25-50% weekly or every other day depending on the tank or fish I'm keeping and how many fish (close to being overstocked) as well as if I'm growing out fry or what I'm feeding them. There are many factors to how much and how often I do it. If you have a tank that hasn't had a water change in a while like at least a month I would do a smaller water change because I wouldn't want to shock the fish. ....since pH usually lowers the longer between water changes. As for 100% water changes I have done close to that doing 90% on grow out tanks or when I kept discus

[fairdeal]

Weekly water changes are mandatory, not optional. The only exception I can think of would be if the tank(s) are very sparsely populated and then you might be able to push it to 2 weeks.. As mentioned already some fish and particularly Tangs do not like large changes and I never do more than 20-25% for them but do 2 changes per week instead of 1 if I can. Small Tang fry like calvus and compressiceps I restrict to 10% at a time.Normal changes for everything else are 30-40%.

Aquarium fish live in a closed environment unlike the wild ones that can move around the lake when water parameters are not to their liking in one area so they are 100% completely dependant on us to make their living quarters as hospitable as possible. As important as water changes are regular filter cleanings. Our fish's very lives are in our hands. Healthy disease free fish make for happy fish.

Here is something I learned the hard and very expensive way - Calgary throws extra chemicals in the water treatment process every spring. To compensate I double the Prime and/or Safe for at least a month and haven't had a problem in the past 4 years. Water changes during this same period are limited to 20% maximum and I do them twice weekly. I have found the extra time and effort well worth it and fortunately my costly experience has not been repeated.

[FunkSolid]

Thanks for the great feedback guys. Why do you think some fish tank people caution others saying "dont change too much water at once it will harm your fish"? Is that because someone told them that, and they are just perpetuating what they heard? Or someone had a really neglected tank, did a huge water change and shocked the fish with a pH swing? Stressed their already neglected aquarium with a massive water change and that harmed their fish?

Edited February 10, 2016 by FunkSolid

[jvision]

A lot of people believe the beneficial bacteria in the tank live in the water, so they think you're taking all the bacteria out... I don't know how many times I've heard someone say that they're going to save all of their water when they move. It makes sense for SW tank people b/c salt water can cost quite a bit to make, but FW is pretty cheap for us in Canada.

[fairdeal]

Most fish are very sensitive to rapid changes in pH. They can adapt to slow regular changes however so if tank water hasn't been changed for say 6 months I would never do a huge change all at once. I would likely do 10-15% every 2nd day for at least a week while keeping a very close eye on the fish as the changes are done. Their reaction to the changes will tell you everything you need to know.

Knowing what your particular fish will tolerate is the key. Discus love 90% changes while Tang fry do best with 10-15%.

[firestorm]

Yes specific fish I wouldn't do large water changes, and others I do! So I think it really depends on what they're keeping and how stocked their tanks are

[DeepArow]

10% because I have really stable water parameters but if something is sick the QT will be 50% wc every 2 - 3 days.

[Mirage]

I like to do 55-80% 1-2 times a week due to having a 10g with 2 juvi. fancy goldfish. I run a filter for a 30g, but I want that water as nice as possible seeing as they are waste machines.

[laurensdad]

I am bad for neglecting water changes on my tanks. I compasate with massive over filtration and a huge amount of live plants I did a change on my 27 yesterday pH was 8 something only other test that showed anything was phosphate at .25 . I normally will do one of filters on the tank and do about 80%

[SomethingIsFishy]

I have a specific day and do 30% on some tanks but 50% on others. HOB filters cleaned weekly and canister filters monthly.

Edited March 28, 2016 by SomethingIsFishy