Question. We have a 455L ( about 120gallons )tank with some guppy's, cardinal tetra, corydora's, rasbora's, hillstream loaches, kuhli loaches and some neocaradina shrimp. The tank is 23℃ ( 73,4℉) ph is about 7,2 /the no³ is about 10 /and the no² is 0/ the amonia test is also 0. Every week we...