@Colin_T are we really suggesting that ph 7.8 - 8 is appropriate for apistogramma?
If you want to keep a species only tank for breeding you need soft acidic water, mine used to be 5.5ph and about 2dgh but the softer the better. Loads of hiding spots and tall wood to break line of sight. Tannin stained helps. Get some surface plants too. You want it warm 27 degrees and a sponge filter bubbling away slowly. IMO 40l minimum for a pair, they need space and lots of hiding spots as females get very aggressive.