help pintail guppy fry over and over

[Matt68005]

It has been going on for 4 months now. It seems they just pintail and die and only a few survive. I have a 30 gallon planted tank with 5 male an 5 female halfback red guppies. They are all big and healthy tank is cycled hardness 200 oh 7.6. Ammonia 0. Nitrite 0. Nitrate 20ish heated to 78 degrees. I feed them a variety flake crushed and brine shrimp. The fry just always pintail. I tried antibiotics kanamacyn and nitrofurazone. I tried parasite clear tabs and also quick cure. I have now moved the fry to a bare bottom ten with a heater and sponge. I dissolved 2 cups sea salt to make it slightly brackish and I dosed with malachiute green. Hoping it's a fungus and I will have cured this problem once and for all. If not it may just be genetic. It's no fun and costing me. Anyone have experience with this and no of a solution other than formalin?

 

[aquandrew]

did you get them all at once? if theyre from the same batch it could be from inbreeding

 

[Matt68005]

did you get them all at once? if theyre from the same batch it could be from inbreeding

Its from the same 4 males anf 5 female red tuxeudo fancies ive had since feburary. I put the fry in the brackish sea salt tank at the rate of two cups per ten gallon and i dosed with malachite green 5ml. they seem to be getting better already. But its still too early. I am gonna dose my second dose today. I heard from a nice older lady thst loves guppies and raises beautiful gups in low tech tanks that it is a fungus. She seems to be right so far so good.....