Is it worth it?

[Essjay]

It's a difficult one. You would need a hard water fish suitable for small tanks. The hard water fish which always spring to mind are livebearers, rainbowfish, central American and Rift Lake cichlids. The two types of cichlid are usually too big for your tank, as are most species of rainbowfish and the common livebearers apart from endlers and guppies which you already have.

For small tanks, Pseudomugils are usually suggested, but you can't get those. I know one member with hard water keeps Sawbwa resplendens (common name Asian rummy nose, not related to rummy nose tetras) but I have no idea how easy they are to get hold of.

 

[Jinx_]

What about scarlet badis? Or are they soft water fish or would they just rip apart my shrimps?

 

[Essjay]

Scarlet badis are tricky fish. Most reports say they only eat live food and won't touch flakes/pellets. Recommendations are for brine shrimp, daphnia and worms such as microworms - in other words very small. I don't know if guppy fry would be too big for them.
The other 'problem' is that many shops sell only males, and males are territorial so that means just one fish.

 

[Jinx_]

Scarlet badis are tricky fish. Most reports say they only eat live food and won't touch flakes/pellets. Recommendations are for brine shrimp, daphnia and worms such as microworms - in other words very small. I don't know if guppy fry would be too big for them.
The other 'problem' is that many shops sell only males, and males are territorial so that means just one fish.

Oh good.. Another fish to avoid lol.

Maybe for the other tank I should get a paradise gourami, then let my guppies breed freely and just feed the thing with excess fry? The 55L will be pretty long so that'll give it space, and I'll make there tiny tunnels just for my loaches.

Yeah, I think that's gonna be my plan.