That sounds like it's about 20 gallons (though I'm not the best with conversions and things
), which is a good size for most of your fish but not good for the shark (as you've acknowledged) or for the sucking loaches - which you may or may not be surprised to hear about.
Unfortunately, this fish, often called the 'chinese algae eater' though it's not chinese and doesn't eat algae after a certain age, also isn't a loach. It's actualy more closely related to the barb-like sharks (red-tailed, rainbow/red-finned, flying foxes etc) and becomes rather aggressive as it matures. This fish, surprisingly for many, actualy reaches 10" - with larger sizes not being unheard-of in the wild. At around 4-6", they start showing the first signs of aggression - usualy towards others of their own kind or similar species. Then they begin attacking other fish - they have been known to trade algae-eating for slime-coat sucking at this point and flat-bodied fish like gouramies are especialy prone to this. They may also go for the eyes of their tankmates - sucking them out - not a nice thought and, as they get larger, will also eat anything that fits in their mouths - your neons won't survive and your danios could become targets as well. Unfortunately, these fish are very often sold in LFSs and promoted as being great algae eaters and good community fish - which they can be, until they reach that certain stage. So anyway, I don't mean to scare you, but anyone who's kept this species for long enough will tell you about them. These two you realy need to get rid of - both for their tankmates' sake, and their own (as they simply get too big and would also kill each other eventualy).
Once the sucking loaches and silver shark are re-homed, the remainder of your fish are alright for the tank but you are slightly over-stocked for your tank's volume so don't add anything else and deffinately make sure you are keeping up with maintainance and water changes.
If you are prepaired to do so, it may be a good idea to also re-home the tiger barbs while you are at it. I think my suspicion that they are an issue with the gourami is correct as 3 isn't realy a large enough school for them. The thing with tiger barbs is that they are well-known fin nippers and will bully and harass everything they can. As such, they are not good tankmates for slow-moving or long-finned fish - gouramies being both of these things (though they can move lightning fast if they realy want to). To avoid problems, it's reccomended to keep 7 or more - not something you can do in your tank as you don't have the space for all these fish - the reason being that, with more barbs, they occupy themselves with each other and don't bother their other tankmates. Furthermore, by keeping them in a group, their hierarchy is such that each fish has another tiger barb beneath it to bully and no single fish is constantly being harassed. You can probably see from your three that one of them is picked on more than the other two or that a single one dominates the other two. In a small group like yours, this can lead to some serious stress-related diseases (which is actualy most fish diseases
) while, in a bigger group, the aggression is devided and no single fish suffers.
If someone comes along and proves me wrong on the tank size - if it's larger that is - perhaps you could just add some more, 3-4, tigers as that would also solve the problem - but not in a 20 gallon. Or, like you mentioned, you could get a bigger tank
.
Oh BTW, male three-spot gouramies have a longer, more pointed dorsal fin, look more streamlined and, as this is a blue specificaly, tend to have bright orange-red pelvic/ventral fins (the feelers). Females have an obviously shorter (half the length), rounded dorsal fin and look deeper-bodied and, when viewed from above, quite distinctly wider. A lot of the differences may eb difficult without practice or other fish to compare to, so, here's a link with some lovely pictures (several variants pictured but they are all the same species and, exluding the feeler color, can be sexed in the same way):
http
/www.aqualandpetsplus.com/Gouramis,%...ichogasters.htm
Sorry about the long post BTW
I find I have a tendency to ramble in detail
