There's a brand of paint called "Sign Painters' 1 shot". As the name implies, it is mostly used for lettering and pinstriping automobiles. Can also be sprayed from a gun with thinner. It's amazingly durable and better than rust-oleum in my opinion. I've used it for a number of applications including my mailbox that endures severe weather climate changes, ice, rain, direct sun, sub zero temperatures etc. i.e. It takes a lot to break this paint down. Probably comes in semi-gloss black flat black but I'm not 100% positive.
I've used this paint on wood and metal alike. One drawback, it does not apply very opaque onto larger areas with a brush (if you plan on using a brush), so you will likely want to apply a few coats. Applies better if sprayed on but watta mess. I would wet sand as a last step depending on how smooth the raw stand is and how much time & energy you're willing to spend. I'm with ShadowVengeance on the idea of using verathane. I think you can get it in semi-gloss. Perhaps this idea for your tank stand is not the best in the universe, but I'ts what I would do since I always have one-shot paint laying around for painting projects that require permanence.