Originally Posted by Fishman007
Never do a 100% wc
. It will take put all your copepods and other critters and alot of you bb.
The water column is fairly devoid of life. There will be some plankton in the water but the vast majority of everything will be found in the substrate and rocks.
That's being said, I wouldn't do a 100% water change due to the shock to your system but a 50% change will drop you down to 10ppm nitrates. Have you thought about a planted fowlr
tank? That will help with nitrates as well.
Lastly, I agree about the sand sifting goby that you shouodnt get one for your tank. But unless you're running a refugium or protein skimmer I wouldn't stock more than 2 clowns and 1 other small fish for a 20g.