I haven't kept any apistogramma yet, and I'm trying to get more info. How vital is it to have low pH and TDS for apistos? I am thinking about 2 male cacatuoides in a 55g. I don't have an RO filter, and I probably don't have the money for one at this point in time. My tap is fairly hard, according to the town water report. The pH is anywhere from 8.1-9.3, and the hardness is 143 ppm (I am not sure if the report is referring to kH or gH, but I would guess gH. There is another report that lists the alkalinity at 38 ppm as CaCO3) Sodium is at 48 ppm (I believe some might be added during treatment to reduce hardness). What I am planning to do is use RO from grocery store filters and fill up the tank with a mix of RO and tap. I am also thinking about running a dedicated HOB filter in addition to my canister that just has peat pellets in it. What would you recommend?