Water changes? How often and how much?

[happychem]

I do 50% weekly (every 6-8 days). I also advise that since it's usually on the safe side. In the end, it's as JSchmidt say, it comes down to NO3. NO3 is your indicator of bioload. Change enough to keep NO3 under 20 or 40ppm, depending on the criterion you choose and scale your maintenance to keep yourself well on the safe side.

 

[Puffernewbee]

I have a 29 gallon and I change about 5 gallons once a month. I check ammonia, nitrites and nitrates weekly and have yet to see the nitrates above 10. I change some of the water just becasue I feel that I need to. Then again, I am not overtaxing the bioload with my fish. :dance

6 neons
5 Harlequin Rasboras
2 Albino cories
2 Fancy guppies
1 otto

 

[bluejay]

hey capnbob:
in short, more frequent water changes under 50% each time won't hurt and is good insurance. The longer you go without a water change, the LESS water you should change when you do decide to do one since the tank water parameters will have drifted further away from the tap params. but read on if you feel like it.

you didn't say your tank size and fish and plant situation, so I'm trying to cover all the bases:
1) light fish load and little to no plants. start out with changing 25% weekly. more frequent water changes the better (actually will keep water params MORE stable if you think about it), won't harm the bacteria. and gravel vac is a GOOD thing, gets rid of waste before they break down. You could do less water change down the road if you get good test kits and get a "feel" of your tank. But water change is simple and cheap and best, get a python or just a bucket on wheels.
2) light fish load and heavily planted w/ co2 and ferts and 10,000wpg. Well you should know what to do already. If not, then just change 50% a week as this 'resets' the chemisty of your water(which is changing rapidly due to the ferts and rapid plant growth, yes maybe you keep nitrates constant but what about all the things you can't test for? they are either getting depleted or are building up)
3) heavy fish load and lightly planted. same as 1 except start out with 50%/week or just 30% every 3-4 days which is better or 10%/day which is best.
4) heavy fish load and heavily planted. Well same as 2, maybe tone down some of your ferts since the fish food/waste will provide some.
5) I recently read you can use a low npk soil substrate covered with gravel (this is actually what I'm doing right now) and heavily planted and only have to change the water 2x a year(which I won't be doing). see aquabotanic.com for more details.

hth

 

[RTR]

Since the half-life of some pollutants in water is ~18 months, no way in Mobile am I going 6 months without a water change. I do not worship at that particular altar. Water is relatively cheap and partials can be made easy, up to automated if you are gadgety.

 

[cambro]

I would agree with JSchmidt. I check my parameters twice a week and if anything is off I do a water change. Nitrates especially. Didn't change the water all last summer and it was a mess! Lost a few fish too. Lesson learned! I test regularly and change when I need to - about once every week or two anywhere from 25-50% depending.

 

[TommyR]

I change out/gravel vac 25% every 5 days. My 10 gallon takes me all of 5 minutes, my 5 gallon maybe 2-3. The replacement water is made the same temp as the tank water.

 

[Aqualung]

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.

Just wanted to correct myself here and explain that this won't work for all tanks. There are lots of variables involved, so there isn't really a "rule" that will work all of the time. Frequent testing of nitrate levels is a good indicator for unplanted tanks.

With planted tanks such as mine (and mine aren't what I consider "heavily" planted), nitrates aren't a good indicator of when to change water. It's better to work out a routine, since plants will use up nitrates, and often people dose with nitrates to supplement the plants. I have never had my nitrates rise above 10ppm, which is already present in the tap water at my new residence.