Suggest a lower level schooling/shoaling fish.

[Byron]

Helpful and thanks. I will bring a sample in one day. I am not using softened water in the tank. I long ago piped in a separate faucet on the incoming line to the water softener for both the aquarium and the few plants I water. I think that lone Serpae is not long for this world. I did not have enough of them and from the looks of things they went after each other instead of any other fish. No other fish showed signs of tail nipping aside from the Serpaes. I don't really mind a lower tank species that's sedate, I'm more interested in one that does not prefer hiding in the weeds. One thing I like about the Harlequins is that they seem to fancy themselves being on full display 24/7

That is normal for Serpae, unless the group is large. When the group is down to one or a few, they can turn on other species, that's the danger here.

The three species in the genus Trigonostigma (the Harlequins) are mid-level fish that will remain out and about unless targeted by some other fish.