My small Test tank is a 12L Nano (around 3Gal) und has 2x13W lightning.I typically suggest 1x a month for the lower range water changes as a measure of good care since many do not test or stop testing after awhile.
But many folks go longer, 2-4 -6 months without them.
Tom Barr;94010 said:I do not think there's any evidence of risk really.
I just like doing water changes and having my plants grow and have the tanks look clean.
hbosman;94020 said:Since I have to use a hose to top off anyway, why not drain it down 50 % first? I suck out mulm in the process. It is, an easier way for me to clean things up.