Hi
that's the exact same dimensions as my tank. I am pretty new to this so I went for things that i thought would be relatively easy to keep although have already made mistakes.
I got my fish a few at a time with at least a two week gap between.
I have 2 silver sharks - really hansome but they do get big
2 pearl gouramis - I was hoping it was a pair but they are a lot bigger now and still no red breast on the one I thought was male so might have to get another.
10 neon tetras ( i had a few casualties early on with these but the remaining 10 seem fine and they are really pretty) Most of my fish are silver and I thought that would look good but a bit of colour helps make the tank look lively.
3 glass catfish - i discovered later that these are supposed to be difficult to keep but i haven't had any problems, apparently they like a good current in the tank which mine does have. To be honest they are a bit boring once you get over the 'wow you can see right through them' factor.
3 silver hatchet fish.
2 khuli loaches - these are great fun, some people say they hide a lot but mine are always out and about, usually together and sometimes just going up and down the tank.
1 gibbiceps - this was my possibly biggest mistake - he is wonderful and I am hooked on plecos now but i didn't realise how big he would get. The usually very helpful woman in the LFS just said 'is it a big tank?' and i said yes because it seems big to me. My gibby is already 5 inches long and he is my favorite fish but i think i might have to get an even bigger tank or pass him on to someone else when he gets a lot bigger. I have since discovered via this forum that there are lots of smaller plecos so I should have done my research first.
My other big mistake was a betta (siamese fighting fish), within a week in the tank he was chasing the pearl gouramis and taking a nip out of their tails. Solution: got another smaller tank on ebay. He now lives in that with one other fish for company.
At the moment all is peaceful and I am really enjoying keeping them.
Moral of the story - don't rush, read up and look at lots of other people's tanks to see what you like.
good luck
DD