if no water feed can be sorted do min 25% water change per week 2 is better the 90 you used to do is to much in one go
use a good substrate i cant understand why people do bare bottom they are missing out on what rays do best dig for food
i like to keep the temp at 84-86 some say lower but thats what works for me
get the rays feeding on hikari pellets
a UV is good peace of mind
a sand filter is a good adition but not needed
no need to add stuff to change the PH rays do fine in lots of different PH just adjust you tank to your tap water slowly my rays have been in a PH of 8.5 now for 2 years they have breed and are doing great its big changes in PH rays dont like
good luck