Water changes? How often and how much?

C

Capnbob

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Oct 19, 2004
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I keep hearing different things about how often I should do water changes and how much water should be replaced. I've heard/read everything from 1/4 tank to 1/10 tank and once per week to once every two months.

So, how much water should I replace and how often?

I use a gravel vac and suck all the junk out of the under-gravel filter, if that's significant in any way.

Thanks!
-Capnbob
 
Generally speaking, you should do at least 20% once a week. I prefer to do at least 50%. You don't want to completely gravel vac, only doing it in segments, like 1/3 the floor every week so as not to lose too much of your beneficial bacteria.

You may need to do more water changes. Monitor your nitrate levels w/ a test kit often at first to figure out how much waste is produced. In unplanted tanks, you want to keep nitrate below 25ppm.
 
Most responsible aquarists who are not lazy change their water in the range of every week to every 2 weeks. This totally depends on how your tank is set up, but in my case, if i neglected weekly maintanance things would go downhill fast.
I do weekly (well 7-10 days ish, depending on how much time i have) of ~50% with a thorough cleaning of my substrate and filter media.

Large water changes are not a problem as long as the new water has ~ the same parameters and temp as your tank water.
 
I think the generally accepted rule is at least 25% once a week. This is plenty to keep things stable and the fish/plants happy. Some people change more, and some less. I wouldn't personally do any less than 25% a week.

I do a bit more than I really NEED to, but it's not inconvenient for me and keeps the water quality high. I change about 25% every other day on average.
 
I do about 50% about once a week to 10 days.

I'd recommend at least 25% every 7-10 days for a fish-only tank, like the 50% approach to planted. If you don't mind the extra work, 50% isn't a bad idea for FO either, just probably not entirely necessary.
 
Well I've been doing 25% every two weeks which seems to work out just fine for my fish.
 
Aqualung said:
I think the generally accepted rule is at least 25% once a week. This is plenty to keep things stable and the fish/plants happy. Some people change more, and some less. I wouldn't personally do any less than 25% a week.

I'm along these same lines. I'd also add that if your usine an UGF I'd be very light on the gravel vacuming as the gravel is your bacterial colony,unless you have another filter too.
Click to expand...
 
I think using arbitrary percentages to guide you in water changes is asking for trouble. You are much better off using nitrates to guide your water change schedule. Most of us strive to keep nitrates below 40 ppm (some prefer 20). I have some tanks that I only need to change 25% every other week to acheive that goal. Other tanks need 50% or more weekly to keep nitrates down. It depends on the tank's stocking level, how much you feed (and how often), what kind of fish you keep, etc.

There certainly is no harm in changing more water than necessary, but if you settle on some arbitrary percentage (e.g., 20%) and it's not enough, nitrate and other dissolved compounds will build up in your tank. Why risk it? Just test for nitrate and develop a schedule that allows you to keep nitrate below some target, say 40 ppm.

HTH,
Jim
 
i do at least 25- 50% weekly or bi-weekly, depending if I have poor water test results or unseemly visual quality. If everything is normal, I change 25% of the tanks once weekly.
 
I usually change my 20-30% of my water weekly, but then my tanks are heavily planted, low tech tanks withmoderate fish loads of small low waste producing fish. If I had a single oscar in a 55 gallon tank or even larger, I would be changing 50% minimum per week without hesitation.

It all depends on your tank setup and fish load. The more fish, the more water needs to be changed to ensure proper health.
 
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