HiVery few aquarium fish are bred in the UK. Most come from Asia where water, heat and labour are cheap. Some come from Germany and some are locally bred, but the number of local bred fish is tiny (probably less than 1%).
A GH of 125ppm is at the top end of soft water and is fine for tetras, rasboras, Corydoras and peacock gudgeons. It is not suitable for livebearers so don't get any of them.
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What are the tank dimensions (length x width x height)?
No to the clown killis. They are too small and require live and frozen foods.
Only get 2 (1 male & 1 female) Honey or Indian banded gouramis. Never have more than 1 species of labyrinth (Bettas & gouramis) in the same tank because they are highly territorial.
Don't add Otocinclus until the tank has been set up for at least 4 months.
Yea ive accepted the soft water issue now and moved on. The honey gourami point you made conflicts with my research, I know the issue you raised is a problem with dwarf gourami but apparently honeys like groups of 4-6 which is why I suggested 4 originally. How can killis be too small but neons not?