I am not a sand fan, My fish are diggers and they will spit it out right on the intakes, if you go sand make sure to have pre-filter sponges on your intakes. if looking to have fry will need them anyways less your filter sucks them up.
and FYI, sand and Impeller chambers do not mix.
Thanks! I have bought two biowheel filters, one for 70 gallons and one for 90 gallons. Will that be sufficient?
I would say do small cichlids which would bring out the 75 gallon. You could do salvini, or cryptoheros myrnae, nanoluteus, honduran red points, apistogramma species, some live bearers, a lil green and wood or lava rock. Just sit and imagine what you want. 75 gallons is a great tank to start with. Good luck
Totally agree with Twonvito and Duane. A 75 gallon is not ideal for large fish that can reach 12-14" in length, even as single specimens. If your heart is set on an Oscar, sell the 75 and upgrade to a 125. The extra space will benefit the fish, and the extra water volume will make managing water quality easier for you. Good luck.