i got 10 new neon tetras for my tank with a betta in it and 3 of them have died i dont know if the betta is killing them or there dieing from the bubble curtain i got it keeps pushing them to the top and it creates a current that takes them a bit round the tank

the betta was kpt with them in shop but i had it for about a week then put them in

Can you give us more information? It could really be anything. Neon tetras are a little iffy on betta compatibility. They are normally peaceful, but some bettas mistake their bright colors as other bettas and may attack.

Tank size?
Other tankmates?
How long has it been running?
When did you get the tetras?
Test results for ammonia, nitrite, nitrate, pH?
Did you acclimate the new fish properly to the temperature AND ph?

Sadly no. Bettas an neon tetras DO NOT MIX! Despite the beautiful colors they display the bettas will fight them. Bettas also see them as brine shrimp, a type of shrimp they eat in the wild, and since brine shrimp are the same size as tetras, bettas will be able to eat the tetras. This person once tried this and his bettas slowly devoured each tetra.