Sudden Bn Death

[webmonkeyuk]

so my beloved BN has just died, yesterday i noticed its belly was getting alittle big but due to it only been about 6 months old i thought it must still be growing but i looked again this morning and it seemed to be bigger so i thought something aint right. Ive had the tank light off over this afternoon but ive just gone to feed the fish and i noticed the little fella up at the top near the heater i didnt have my glasses on so i couldnt see properly but when i come back i realised he was floating upside down and was dead it looked like his bottom was blocked as there was a orange thing half sticking out. Ive tested the water and all is fine so what could it be? or is it just one of those things? theres 2 bits of bog wood and ive had cucumber in the tank so theres enough food

 

[bridfish]

i had that with about 14 of my baby ones don't know what it was.

but does anyone know why half of my baby's die. i get about 40+babys and with in a week I've only got 10-20 left.
all i have in the tank is a male 2 female and about 20 babys some 6 months old ready to be sold when i know the sex of them.