What are the tank dimensions (length x width x height)?
What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website (Water Analysis Report) or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
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Glolight tetras should be in groups of 10 or more like other tetras.
Avoid dwarf gouramis (Colisa lalius) and all their colour forms. They regularly carry Fish TB and the gourami iridovirus, neither of which can be treated. Most other small species of gourami don't carry these but can catch them.