General Care Discussion :: Water changes

[gbr_mx]

Hi, I have a question about water changes, I have a 2" res in a 40 gallon tank, with a fluval 406 filter. I recently changed from a 20 gallon tank, I used to change all the water in the tank every 4 days, now I don't know how often to change the water and how much water I should change. Thanks.

[ljapa]

Hopefully you have a nitrate test kit to let the nitrate readings help guide your water changes.

Unless those readings are super high, you are probably safe with a weekly 20 - 40% change.

[gbr_mx]

ljapa - Thank you for your answer, I did a 50% water change last week because the water got very cloudy, it got a little better , today I did a 10-15% water change, I think Im going to do 10-15's every 2 or 3 days until my filter develops benefitial bacteria, what do you think?

[ljapa]

It sounds like your tank is still cycling. I've not experienced it with my two tanks, but a cloudy period is a frequent bacterial bloom in the establishment of the nitrogen cycle. It should clear in a few days.

The general recommendation is to not change water during a cycle, but I'm not convinced. Everything I read says that the nitrifying bacteria are surface dwellers and stick to the biomedia, substrate, etc... If you pull out too much of the ammonia and nitrite in water changes, you may cut down on food and make them take longer to establish, but they will still establish.

I would stick with small changes until testing shows just nitrate, no ammonia or nitrite. Then, I would let that nitrate reading guide your changes.

I do a 20 - 30% change weekly. I also have filter with a canister filter plus a refugium with extra media and plants that pull nitrates out of the water. My nitrate readings hover around 5 - 10. In the fish only 20 gallon that was Tobi's old tank, a 25% weekly gives me a nitrate reading closer to 20.

[Starscream]

Is there any kind of formula for this?

I'm thinking like .25 nitrate = 10 percent change
.50 nitrate = 20 percent
.75 nitrate = 30 percent change

That would be awesome, I have wondered how much water to change at what nitrate level also.

[talal]

I vacuum the river rocks pretty hard to get all the funky stuff out and I always end up doing a 50% water change every week and my turtles, fish and shrimp all seem to be okay with it so far