Hi..

[...Tetras...]

A 120L tank might limit you to one Tetra species but of course than more of
them..

[...striking tank mate(s)...]

(1) Betta splendens

In my mind a good choice..

(2) A pair of Honey Gouramis

Ditto but at the moment the most gouramies sold in Europe seem to be of bad
quality, they're often ill and early dying. Try to find a regional hobby
breeder..

(3) A pair of Kribensis. (I'm not sure these will be OK with such small
ultra-peaceful tank mates since they can get up to 3 1/2 to 4 inches in
size. Also, despite their reputation for being relatively peaceful,
being cichlids I suspect they will still guard and hold a territory
quite aggressively if they breed.

Peaceful as long as they don't breed but growing up respectively adult kribs
are always breeding and breeding kribs are little devils were even able to
terrorise a 300L tank all day long without getting tired..

Wouldn't recommend to combine kribs with cory cats because both are bottom
fish, both love caves but a 120L would never offer as much refuges as
needed for the cories to hide..

Free water tetras and kribs were no prob..

I do have a 15Gal (UK) tank which is
currently empty so I could transfer them if their aggression gets out
of hand. I don't know, maybe this idea is a non-starter.)

Hmm.., you're responsible for the fish you buy. A 15g were to small for a
couple of kribs..

(4) Killifish

Is the small and colourful Aphyosemion australe available in the UK..? I've
the golden form. They're great fish but even able to catch guppy babies.

(5) Apistogramma Dwarf Cichlids

Some of them are soft (and acid) water fish..

(6) Something else...

Well don't know this or any other species of the genus "Something"..! ;-)

Any ideas, comments, or thoughts would be most welcome!

How is your water..?
--
cu
Marco