I recently finished the cycling process of my 12 gal tank - all numbers came out great and I have been able to add in all of the fish that I want while still maintaining great testing numbers.

So now that I have a fully cycled, full of fish tank, how often do you recommend that I do the 25% water change? I've read anywhere between every 2 weeks to once a month, so I wanted to hear opinions. I have a pleco if that helps to make a difference (bristlenose albino).

Also, once a tank is fully cycled, how often do you recommend that I perform the API testing again? Once a month, or do you think more often than that?

Thanks!

I try to clean mine once a week though sometimes I don't get time so its every 2 weeks. It really depends on the bio load in the tank but I would say if you have time then once a week. I also never test my tanks but my fish are fine and I add seachem prime every water change

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36 gallon - 6 Rummynose Tetras, 6 black khuli loaches
20 gallon - 4 peppered cories, 5 danios, 4 glowlight tetras
10 gallon - cherry shrimp, jungle val, Red Ludwigia, dirted

I use the mothods in the link in my signature.

I just knew the worked but a few years back actually took measurements finally (about time it had been literally decades). Which verified the system worked.

With those measurements if have unmeasureable nitrates and phosphates plus a high PH (indication low carbon dioxide). During the cycle I experienced short (1 day or less) very low spikes in ammonia or nitrItes but an initial spike in nitrates. which indicates a "planted" cycle where the plants are consuming ammonia over nitrates.

I also measured (with peat moss in the substrate) that hardness remaind low and constant for 2 years or so. (kh 4 degrees gh 9 degrees)

I also do no water changes.

To limit the build up of things like nitrates with no plants you can use water changes. Just don't expect nitrAtes to be low (under 20ppm or so) at any convienent level of water changes.

Still that's just my .02

I do 25% PWC's weekly and change the filter media once monthly, FWIW

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FW 10G, 5 neons, 1 fancy male guppy, BNP, pond snails, ~80 RCS. Camboba, java moss, java fern, willow hygro, ludwigia repens, dwarf sag, anubias nana. AC50, 50W heater, Current USA Nova Extreme 2x18W T5HO.

"Give me your penchant and I shall grant you deliverance." - Falcor

I do at least 25% water changes weekly and I don't clean out my filter unless it gets slightly clogged up. It's too much of a PITA for me to clean it like a HoB. after the tank is cycled, I only test nitrates if the fish are acting funny.

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Frontosa Fanatic

I do 25% every week, maybe every second week if I'm working a lot.

A bristlenose makes that unavoidable by the way - they are great fish but waste machines.

I clean the filters by rinsing the sponges (all mine are aquaclears or modified for sponges) in tank water I've removed. I do it when they look clogged.

Personally, I don't test water, but I did for a long time, before every second water change. It allowed me to get an understanding of what was going on. With time, you get an eye for what's going on in a tank, but that isn't something you can do when you are new to it. The test kits can be your eyes - you should use them when you are wondering what's going on in the water.

What is your stocking level in that small tank? If you are anywhere close to being maxed out or overstocked you will have a very delicate system. Based on that, I would test for nitrates at the end of the week and see where they are and perform the water change based off the result. Values below 20ppm are desired "after" your water change. If you are hitting 60-80ppm at the end of 1 week and only do 25% you'll never get your tank below 20ppm to start off your week.....and nitrates tend to increase as you go through the week.

Nitrates will decrease roughly the same percentage as your water change. Ex. a 50% water change will mean you'd reduce your nitrates by 50%.

I do 50% weekly water changes in all of my tanks.

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"Being ignorant is not so much a Shame, as being unwilling to learn".-- Benjamin Franklin

I do a minimum 50% water change weekly as well as test at least once a week or more.

It's a pain to do it (buckets!) but it seems to prevent any problems since it is always in optimum condition. A healthy tank makes it less stressful for the fish.