It's really easy,well for most of them lol,once you familiarize yourself with the different species.There are five known species and you can start by taking a look at some of the stickies at the top if the page.
Oops....when I first saw this thread I assumed it was in the datnoids section which was why I suggested reading the stickies...Just go into the datnoid sub forum and check out the stickies there.....
Almost 99.9% of the time there Gona be Indo dat 26% ntt or ngt 36% silver and less than 5% are CT and 1% are ST. But indo's,ST, and CT all look the same but st and ct have much thicker bars,always stable, and have a different tail marking than indo's. AT or "silvers" are pretty easy to ID there Gona be silver. And some need brackish water as they get bigger. NTT and NGT have really thin bars and have a darker look to them. Here's some pics that helped me learn the difference.