There are several good Loaches for that size tank but with eight angels already you really don't have room. Instead of adding fish to take care of the problem lets see if we can help get rid of the snails first.
Snails are good for your tank. They eat dropped food and keep the substrate loose by crawling around in it hunting for food. The problem comes if you have a population explosion. Snails grow according to how much food is available to them. They are frequently a symptom of over feeding. Weekly 25% (or larger) water changes, thorough substrate vacuuming and not over feeding (a fishes stomach is the size of one eye) will go a long way to keeping them from multiplying so fast. I know angels are piggies and will eat as long as you feed them and beyond if possible. The more they eat the more waste they produce . The more food dropped and waste added to the tank the bigger the snail population explosion. One way to get rid of them now that you have them is to bait them. At lights out drop a piece of lettuce, zucchini etc in the tank. In the morning before turning the lights on the veggies should be covered with snails, dig it out and throw the snails away. with careful maintenance and baiting you should be able to knock the snail population way down.
If you still want a loach (I hate to see people buy a fish they really don't want just to solve a problem) Yoyos (Botia almorhae), zebra Loaches (Botia striata), Polkadot Loaches (Botia kubotai) get about 5 inches and are excellent snail eaters. Then there is the tinly Dwarf Chain Loaches(
Yasuhikotakia sidthimunki) which might be a better idea for your tank. They get to be about 2.5 inches. Here's a good place to research for what you want
http://www.loaches.com/
Carol