A little back story. I had 3 ABN in my 90g tank and I could not tell what sex they were.I noticed that one of my ABN ancistrus (the larger of the three) got really fat. The other two, I was told, had the ABN longfin gene. I was both excited and worried - she could either be full of eggs or was sick and was going to be the next casualty to the bloat that was decimating most of my tropheus.

I figured I'd give it a few days and see if she lays eggs, but that didn't happen. I figured they all might just be females, since none of them had prominent bristles and the other two were quite young. So I moved all three in a 10g tank and borrowed a long fin ABN (unknow sex) from a friend and put it with them. I put a bunch of pvc pipes of varying sizes and some driftwood and rocks in there.

In two weeks I saw a few fry swimming around with yolk sacs still attached to them. I am very excited especially since this was my first successful spawn with ABN and after the downer with my tropheus casualties. Interestingly, it seemed they spawned in a shell out of all places! Shelldweller ABN!

Unfortunately, I don't know who the dad is (I'm assuming the mom is the big fat one). Now I'm curious to find out if any of the fry will turn out to have longfins. How do the genetics of the longfin ABN work? If the dad is not the longin ABN but one that is regular with longfin gene could some of the fry have lonfins?

I had a spawn a few months ago where the female was longfin and the father was shortfin. The fry was 50/50, Now if both are shortfin but carry the longfin gene, you may have about 20% longfins.

If you breed back one of the fry when it gets older to one of adults you have you will probably get 30/35% longfins, Each generation will give you a few more. But as slow as they grow, that can be a year before the fry will be big enough to breed.

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I believe the female was regular fin and the dad (I think) is regular fin with the longfin gene. I guess in that case a very small percentage - < 20%?