Dying tetras?

[labrakitty]

I have a 120 Litre tank (approx. 29 gallon) with: 1 lace gourami, 2 bristle nose, 1 peppermint bristle nose, 10 corydoras, 2 otos, 1 yoyo loach, 3 ember tetras, 2 cardinal tetras and 1 pristella tetra.

When I first got the tetras, I had 6 cardinal and 4 pristella and 10 ember tetras (although they were in a different tank).

Over about 6 months the cardinals and pristellas gradually would just die off one by one for no visible reason (apart from 1 cardinal dying of white spot, but the others survived.) The same thing happened with the embers but a lot faster, they were all happy for a while then they just started to disappear. Maybe because they are very tiny they don't live very long?

With the other tetras I've tried buying more cardinals and diamond tetras, but the same thing happens after they have been in the tank for a while after being quarantined. Any ideas why?

[Zagz]

Water parameters would be extremely helpful as well as any physical signs, changes to the tank etc. There is a list of questions in the sticky at the beginning of this thread that the answers to would help. Depending on the size of your tetras, the gourami may be attacking them.

Also you have a lot of bottom feeders in that size of tank. Your yoyo should be in a group of 3 but you have no room for him. I would get rid of 2 BN plecos and some of the cories or the 2 otos.