I agree. 25 Liters is too small. and even experts use 60cm long 54 LitersFor long term keeping, 80 liters (20 gallons long, not high) is recommended. Some experts will put pairs in as small as 40 liters temporarily for breeding, but not for long term keeping.
25 liters is just far too small for apistos. Nano fish or inverts would be good for this size.
yuck...Or everyone's favorite...a Betta
I’ve kept a wild betta imbellis in a 5g, not a bad choice IMO.yuck...
See Parosphromenus = Licorice gouramiThere are some interesting blackwater gourami that are quite small.