My shout's on this being that Nephasth fella. Call it a hunch.
Thus, being that he's such a lovely, cuddly fella I help out gladly:
It depends if you are aiming on petting tropical or cold water fish. For a tropical fish tank, maintaining a warm environmental temperature ranging between 75 and 80 °F (24 to 27 °C) enables the fish to thrive. For cold water fish, when kept in a household aquarium, they do not require a heater and are quite comfortable at around 60 °F (15 °C).
Thus, tropical fish may present less of a challenge to your design brief as opposed to cold water fish, given the reduced cooling requirements.
As for the baby oil, that is an area of your subconscious that only people on Death Row and Crack can aspire to understand.