The venezuelans also seem to be much less active and are prone to hide now after we added the pandas but not sure if that is a related issue. The pandas are actively foraging but the venezuelans do not anymore except when fed. The three pandas are a collectively tad larger than than the venezuelans, with the largest venezuelan about the same size as them.
There has been no recent deaths in the tank but we lost two otos during week 1 when the tank was first setup.
Water Parameters
a) Temperature range = 27 degrees Celsius (we live in the tropics so there's no heater in the tank)
b) pH = 7.6
c) GH = 143.2
d) KH = 8
e) Ammonia, Nitrate, Nitrite levels = 0,0, less than 5ppm
f) Water change frequency= 10% weekly tap water (treated with Seachem Prime)
Tank set up
a) Size = 17 gallons (60cmx30cmx36cm)
b) Substrate = gravel
c) Filtration = fluval c4
d) Food used and frequency = Hikari wafers + guppy food twice per day
We've removed the carbon and dosed Seachem Paraguard for four days but plan to discontinue that as it seems to really make the venezuelan corys lethargic. Have reintroduced the carbon and did a 20% water change to help get rid of what's left of it in the water. There's no white spots on any of the fish so that rules out ick right?
We do not have Prazipro out here but we've ordered a bottle of Eiho Prazi Gold (which also lists praziquentel as its active ingredient) which we are not sure if we should be using. Should we use aquarium salt instead and if so at what concentrations (conflicting info on the internet

Also, we have aquarium sand ready to replace the gravel (RIO Amazon) but am thinking of holding off the change until we've treated the flashing?
Thanks in advance.