Dwarf gouramies preffer to set up a territory in the upper layers which is also where the danios would be spending most time. In fact, most of the common gouramies besides croaking and sparkling are the same. For this reason, I'd say you are better off with somthing other than dwarfs. BTW, leopard and zebra danios are, in fact, the same species dispite the different scientific name. So you don't need to add any more. That way you'll have more space for other fish.
Besides croaking gouramies, there are other mid-dwelling fish you could try.
Mollies and swordtails, in particular, spring to mind. Mollies get to 4" easily so keep that in mind. If the tank is heavily planted, you can get away with just a male and female (assuming you want fry) and still won't have to worry much about the female getting chased around and stressed. If you aren't interested in fry (remember they will multiply if ythey breed and the fry have places to hide in the plants), a couple of males or females would work instead. Obviously, if you get females, they may be carrying sperm so you may still get some fry at the start but none after about 4 months.
With the swordtails, which I love, males only get to about 2" but they don't appreciate the company of other males. You would probably be best off with a trio. The females get to about 3". You could also go for all females but keep in mind their larger size. Don't get all males!
If you don't want livebearers, you could try 4 female bettas. Some people will say they are concerned about the danios nipping them but, honestly, zebra danios aren't realy nippy and, in a group that size, they'll be more concerned with each other.
There's plenty of barbs (golden, ticto, checkered, rosy), rasboras (fire, harlequin, clown) and tetras (phantoms, emperor, black skirts/widows, x-ray/pristella, - possibly glowlights, rummynoses, neons or cardinals depending on just how hard your water is) that, as a big school, would look fantastic. They won't be large fish though so may not be quite what you were after.
Then there's rainbows - have you considered trying some blue/neon dwarf rainbows? These stay quite small (about 2") and are a bright blue color. They are schooling fish though so they have to be in a reasonable school. I'm not sure how many cories of what type(s) you have but, with all those danios as well, you may possibly be over-stocking. The same applies to the schooling fish I mentioned above. Oh and there's also the thead-fin rainbow to consider. Not that brightly colored but very interesting fin shapes.
You could try a pair of american-flag fish. These lovely killis get to 3" and the males have wonderful color.
You could get a pair of cherry barbs as well. Though they are small, males are a bright color and make very interesting additions.
If you are still interested in rams, go for bolivians. These are almost the same as gold rams but less fragile, slightly more aggressive and will do absolutely fine in hard water. A pair will even breed for you. They are, admitedly, not quite as colorful but I think they make up for it in character.
Besides croaking gouramies, there are other mid-dwelling fish you could try.
Mollies and swordtails, in particular, spring to mind. Mollies get to 4" easily so keep that in mind. If the tank is heavily planted, you can get away with just a male and female (assuming you want fry) and still won't have to worry much about the female getting chased around and stressed. If you aren't interested in fry (remember they will multiply if ythey breed and the fry have places to hide in the plants), a couple of males or females would work instead. Obviously, if you get females, they may be carrying sperm so you may still get some fry at the start but none after about 4 months.
With the swordtails, which I love, males only get to about 2" but they don't appreciate the company of other males. You would probably be best off with a trio. The females get to about 3". You could also go for all females but keep in mind their larger size. Don't get all males!
If you don't want livebearers, you could try 4 female bettas. Some people will say they are concerned about the danios nipping them but, honestly, zebra danios aren't realy nippy and, in a group that size, they'll be more concerned with each other.
There's plenty of barbs (golden, ticto, checkered, rosy), rasboras (fire, harlequin, clown) and tetras (phantoms, emperor, black skirts/widows, x-ray/pristella, - possibly glowlights, rummynoses, neons or cardinals depending on just how hard your water is) that, as a big school, would look fantastic. They won't be large fish though so may not be quite what you were after.
Then there's rainbows - have you considered trying some blue/neon dwarf rainbows? These stay quite small (about 2") and are a bright blue color. They are schooling fish though so they have to be in a reasonable school. I'm not sure how many cories of what type(s) you have but, with all those danios as well, you may possibly be over-stocking. The same applies to the schooling fish I mentioned above. Oh and there's also the thead-fin rainbow to consider. Not that brightly colored but very interesting fin shapes.
You could try a pair of american-flag fish. These lovely killis get to 3" and the males have wonderful color.
You could get a pair of cherry barbs as well. Though they are small, males are a bright color and make very interesting additions.
If you are still interested in rams, go for bolivians. These are almost the same as gold rams but less fragile, slightly more aggressive and will do absolutely fine in hard water. A pair will even breed for you. They are, admitedly, not quite as colorful but I think they make up for it in character.
