i'm assuming your tank is about 2ft, as my 2ft, by 1ft by 1ft tank is about 15gal. and your sig says its a 15 gal tank.
well really before you think about adding anything else you need to think about re homing some of your existing fish. working on the inch per gallon rule your current stocking is not good.
the first thing that needs to go, is those
clown loaches, who grow to an average size of 7-10 inch and can get as large as 14 inch, so those 2 clown loaches on their own are too much for your tank, and really clown loaches should be kept in groups of 3 or more.
firemouth cichlids apparently can get to about 7inch, with males being bigger than females. so if we assume 5inch for the female, thats still 12 inch of fish at adult size leaving you with 3 inches available. so i would recommend re homing them too.
your remaining stocking is probably, doable, although you need to keep in mind that neons can be fin nippers and may make your bettas life hell. ideally he would probably be removed to a 2-5 gal on his own or maybe with a cory for company?
and you also need to keep in mind that with 2 female and 1 male swordtail, you will soon have lots of babies, most of them will not survive with those tankmates, but some of them might manage it and that will only increase your stocking more.
also its not a good idea to keep gouramis with bettas as they are can get aggressive with each other. it has worked in some cases, but not recommended. although if you remove your betta this would not be a problem any longer.
