Help! My RCS keep dying-
First planted tank, first aquarium. 20tall with T5HO 6700k & 10,000k bulbs. 50/50 mix of fine black eco-complete and fine black flourite sand. An aquaclear HOB 50gal with polyfiber & ceramic bio media, a small sponge filter.
Java ferns, pennywort, crypt spiralis, hygro kompakt, watersprite, and some riccia floating.
Fishless cycle completed.
Started getting some algae, so about 1.5 months ago I got 75 RCS. They were the first fauna I put in. They seemed to do very well. Added 5 nerite snails a few weeks later. RCS still doing fine. About two weeks ago I added 10 purple harlequin rasboras & two otos. Now for the past week or so I've been finding at least two dead RCS on the substrate a day. Started testing daily and am getting healthy results-
NH3 - 0ppm
NO2 - 0ppm
NO3 - 5ppm
I did notice that my pH which was steady at 7.5 - 7.6 went up to 8.0 and is holding steady there now. I got a GH/KH test kit as someone told me this was important for keeping shrimp. I don't understand the results though. The KH test resulted in 6 drops, 107.4ppm, GH was 8 drops, 143.2ppm.
The other fish are healthy and active. I can't imagine that rasboras or otos would go after shrimp. And if they did, wouldn't they eat them and not just leave the corpse laying on the substrate? I can't figure out what's going on. Anybody have any insight?