I presently have a group of seven in a tank along with a group of dwarf rasbora (
Boraras brigittae). I have had this fish twice before, last time was six years ago, and I raised several fry from spawnings then.
There are four species in the genus
Sphaerichthys.
S. osphromenoides is the most commonly seen.
S. selatanensis is near-identical but has an additional vertical white/cream stripe and is much less common.
S. vaillanti is very rare in the hobby. Fourth is
S. acrostoma, larger and also rarely seen in the hobby. I have
S. osphromenoides and you may have seen this recently available (which may be why you've asked,
); being wild caught (unless one has a local breeder), these fish will be available probably once a year, during the collecting season.
Always buy a group; they are social fish, with interactive behaviours that are enjoyable to observe. And you will likely get male/female--these are easy fish to spawn and raise. I have severn now, but I would say six is minimum.
This is a delicate and sensitive fish. First requirement is very soft water, on the acidic side. Zero GH and KH, or close, and let the pH drop naturally. Warmth is also essential, in the high 70's to low 80's. I have mine at 78-80F. If the source water parameters differ significantly from the parameters of the established tank water, do smaller and more frequent water changes rather than larger weekly. I'm lucky to have very soft water out of the tap, so I change half the tank weekly.
A planted tank is good, provided the light is not strong. Especially important are floating plants, the surface can be thick with floating plants. Water Sprite (Ceratopteris cornuta) is ideal, as it will easily cover the surface and the root masses will get large. Like all gourami, this species loves to cruise among dangling roots and branches, continually looking for microscopic food. And a good cover of floating plants with thick roots will mean fry if you have male/female. The first two species I mentioned are maternal mouthbrooders, the second two paternal mouthbrooders. I've only had my present seven for a few weeks, but I have noticed an obvious pairing happening, so hopefully I will see spawning like I did six years ago. I'll go into this more if you ask.
Lighting should be on the dim side, so either have lower plants that are good with less light (mosses, Java Fern, crypts, pygmy chain swords) or you can go true blackwater with no lower plants and lots and lots of wood and branches and leaves and thick floating plants. I have my group in a 29g, photo attached. Quiet filtration (I have a dual sponge filter) to avoid water currents; these are after all fish from ditches, swamps, peat marshes.
Lots of wood is good. And dried leaves. Autumn is upon us, and a good time to collect fallen dead leaves from a safe location (the back garden if no insecticides are used, or a forest). Oak, maple, beech are safe; I believe pretty much any common hardwood tree is OK. I have an oak tree and every autumn I collect hundreds of fallen leaves, dry them, and bag them to use in various tanks. These also provide excellent first foods (infusoria) for all fry whatever species. Organic matter will add essential substances and bacteria to the water that are beneficial in preventing skin disease too, something common with these fish.
Keep the tank well covered to maintain warmth in the moist air above the water; like all gourami, these breathe air as well as normal gill respiration.
Feeding shouldnot be difficult; mine have always eagerly consumed dried foods (good quality flake), frozen daphnia, and frozen bloodworms once a week. I've never bothered with live foods, but if you can, fine. Daphnia and wingless fruit flies would be ideal. These fish do naturally feed from the surface, but they will browse the substrate and every surface searching for food, and usually eat any that manages to sink to the bottom.
Tankmates are OK but they must be very peaceful, small and sedate. Many of the rasbora work well. I mentioned
Boraras brigittae, and previously I had a shoal of
Trigonostigma hengeli.
T. espei is another good rasbora. The third in this genus,
T. heteromorpha (common Harlequin) is a bit large in my view, and perhaps a bit more active. If space is sufficient, other small gourami can be added, like the pygmy sparkling gourami (I've had these and the Chocolates in my 70g, both spawning regularly), eyespot gourami, licorice gourami; but avoid any of the "common" gourami species as they can be more rambunctious, larger, and more of a disease threat.
Feel free to ask questions.
Byron.