I dont know about neon tetra diseases. I have 12 neon in a 20g tank and they look stunning and awesome. 6 of them are with me for about 8 months and the other 6 are woth me for about 48 hours and they are eating and all.
Black neon tetras are just like any other tetra when talking about habitat. They will enjoy shade areas, leafs and dark substrate with black water. They will feel confortable and the strong light wont let them blind because of all these factors.
Give ypur tank some crew, like shrimps, snails and cory or pleco (they will be nipping larger fosh fins)
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