A 75gallon aquarium FILLED to the brim WITH an Above basking area IS the BARE minimum for ONE ADULT MALE red eared sliders. Females need a 125. A pair 150. You need HEAVY filtration for them. I have had a couple over the years, and now I only have texas map turtles. But I know now that those were the messiest turtles ever. They pooped like a baby they ate like a baby. Again Check what you have. One 75g=one MALE. Males size tend to go up from 5inches-8inches. Mine was 5inches and STILL in a 75 gallon he was a pig. You also have to watch for ammonia readings. Water should be soft/acidic, as it helps prevent fungus. YOU STILL need a dry area. A turtle dock DOES NOT work for this. Again build an above tank basking area which will stay dry. put heat lamps and uvb/uva lights on top.

As for the frogs, just dont mix any animals together buddy. Not even different color morphs. ONLY THING I would EVER say you could POSSIBLY mix together would be the "xenopus" family. Meaning african clawed frogs and its varieties. BUT THATS IT. Nothing else can go together. Trust me even if you take it to the vet, it wont kill all the parasites the animal has. Just go with what people have been telling you. No diff color morphs together, no diff species. Nothing.