Wanting to do a saltwater tank
Nanos are very doable nowadays but they are much less forgiving than large systems and the livestock selection is much more limited. Starfish for the most part donít do well in captivity other than serpent stars. Seahorses need species specific tanks with lower flow and lots of things to grab on to. Clowns are pretty easy as are most crabs and shrimp. If you want a reef youíll need good lighting. Iíd start by doing research on basic as setup and care (testing, salinity, top off, hitchhikers, live rock, comparability and such) and go from there.
20 Gallon SPS reef
29 Gallon FW "fat catfish" tank
20 Gallon Long Dart Frogs "Zig" and "Zag"