Good choice switching to tropical aquarium, much easier to maintain tbh.
You're saying you have a 4 foot long tank so that could be anywhere from 45-60 gallons depending on the height. Regardless you have many choices of fish and plants that you can add (if you choose to go with live plants). I have had neon tetras in the past and they are pretty good fish for temps that don't go over 76 degrees. If your tank is warmer than 76 degrees you should check out cardinal tetras. They are bigger, more colorful, and definitely more expensive. It's up to you whether you choose neons or cardinals. You can also get a pleco, which cleans algae from plants and walls which is pretty helpful. Other fish you can consider are platies, mollies or swordtails that work well in a community tank. Tiger barbs and clown loaches might be worth looking into as well. In my tank it is mostly tetras and 2 angelfish which are great. Never get tiger barbs and angels together in the same tank though because the barbs will nip the fins of the angels. At then end its all up to you. There are plenty of freshwater community guides out there that you can research. Good luck.
I have a small clown loach in my 24 gallon and he is just fine. J4M3S has a 50+ gallon so that is more than enough. Clown loaches are fish that do not show significant growth until you have them for 2-3 years so they are a great fish to have.
Glad you bought some rummy nose tetras I'm planning on getting some of those soon. Plecos are very not that expensive either. Pretty cheap tbh.
errrg not clown loaches,they get 12" should be in 5-6ft tanks (100gal+)