Qays, I have a 20 gallon high, so I can tell you the dimensions are 24Wx12.5Dx16H, in inches.
Seth, I don't know what kind of fish you're talking about when you say "midget suckerfish", or "dwarf catfish". These are common names and could refer to any number of different species. If you don't already know the scientific names for them, then either post a picture to ask people here to identify them for you, or do a search on google to find pictures that match what they look like to find out the scientific name. Its important to know what you have so you can know how large it will get.
You said it has had fish in there for 4 months, have all these fish been in there for that long? And why are you saying the tank is in distress? Maybe you should describe your problem better. Going on no information except what fish are in there makes it tough to diagnose a problem, especially if you haven't described the problem.
Some things about the tank are good, it may need improvement depending on what you've left unmentioned. None of the fish you mentioned is too large for the tank, which is good, except maybe the two that we don't know what they are. The betta isn't really compatable with the other fish and is probably spending a lot of time hiding, and you may be having trouble with the rams being too aggressive towards the "midget suckerfish" or the "dwarf catfish", but I'm only guessing since you didn't mention what types of problems you've been having. Let us know what kind of filtration you have on the tank, how often and how large your water changes are, and what you have observed about the fish's behavior towards each other, as well as whether everything looks healthy or not. Also, do you know if your rams are male or female, and how are they getting along? And the betta, is it male or female?