My Ranchus! Are ~~~ Wierd~~, help~ Options

[javanoob]

hi i have 2 ranchu they are around 18 months old.
i bought them when they are very small.

i feed them only 1 time everyday but quite alot. for their size.
my filtration are good , the water quality are good too. i have tested with all the kits. for ph amonia nitrate nitrite etc.
after so long of rearing, i have realise my ranchus have only grow up abit and is stuck at a certain size
around 6.5 to 7cm in length including tail. which seems to be very small. but they do look fat for their size.

i have rare them in a 2inch tank, so the amount of size for growth is ample. i dont understand why dont they grow?

2ndly, one of the ranchu always ahve this problem, part of its rear tail always have a black patch of about 1 cm long, that grow out of no where and disappear after a few days or week. and will reappear some days or weeks again. its doesnt seems to affect my fish abit, but i am curious what kind of diesease it is?

anyone help?
10s

[CyberET]

i think u mean 2ft tank. its actually small..
the black patch of the rear tail, is it at the bottom lope?

[javanoob]

yea its at the bottom part.
2 ft tank might be small, but its very spacious from the size of my fish.so i am wondering why dont they grow.

[CyberET]

possibly fish sits at the bottom too often