This is on my main tank which is a 40 gallon with a gibbiceps who is a messy feeder
I was very suprised to get an almost zero nitrite reading

My second tank, a 30 inch heavily planted set up with ottos ect is also zero using siporax but would expect that.
I will now change my third tank over from a sponge internal to an external with sintered glass too as that has a nitrate of10 mg per litre.
This tank has a clown plec and gold nugget plec.
Is 10 mg per litre OK for nitrate ?
I also test for phosphate and am getting .25 to .5 mg per litre in all the tanks.
Is phosphate harmless to plecs?