SW is usually more expensive then
FW, as there is more need for filtration, the fish are usually more expensive and there are additional purchases you have to make, like bags of marine salt. Impossible to say how much one costs tho; depends on what size tank, what type of filtration, what sorta fish, etc.
Otos are
FW only. Mollies are one of the few aquarium fish that can go either way; most fish are
FW, brackish OR
SW. Otos can be compatible personality wise with mollies, but if you keep mollies in brackish or
SW then no otos. Otos also don't do well in the hard water mollies prefer.
Oh, and what kinda fish do you have? I forget. Heh, if I waited for my fish to leave me before going
SW, I might get pretty impatient
LOL plecos and clownfish can easily live 20 yrs or possibly more if well kept, angels should hit at least a decade.
