it would depend on your stock, bio-load, filtration, feeding, subtrate, etc., but all my tanks are done once per week.

I do a 50% water change minimum on all my tanks weekly. Grow out tanks with fry get 50% twice weekly. I swear by this method. That includes gravel vaccuming . My tanks are always crystal clear and algae free. Fish stay healthy!

Never tried 50% weekly. I thought that was either too excessive and unnecessary OR might stress the fish out. I should give it a try in a tester plant tank with some hardy fish.

just curious, do you use tap water (or RO or something?) And what size is your tank? So we have an idea of the total volume being changed. Thanks grankag!

I use tap water only and run a variety of tanks from 20 -80 gallons. I have not considered using RO but it is something I will need to research. Now you have me wondering if I should try 25% instead. I can only say that the 50 % has been working so I had never considered another method.

i do about 50% water changes also in all my tanks, also, ro water, would not be a good idea, as alot of trace elements,/minerals are removed, to that affect.if your fish are cichlids