I have not read anything on if the long fin or any of the color morphs are mendelian traits. But bases on people's experience the long fin trait could be
"""""If I were to succeed in spawning two of the long-finned babies together, would it be correct to expect that three quarters of the babies would have long fins, one quarter would be albinos, and three sixteenths would be both albino and long-finned?""""
----Yes, I got the same thing working out a punnette square, but it is only true if the trait is mendelian and each is controlled by only one gene and if the color morph gene is separate from longfin gene.
""""""""Would it be possible, in future generations, to find a baby with a double dose of the long-fin trait, and obtain a spawn that would be entirely long-finned?""""""
----yes very likely if longfin is an mendelian trait, but you still have to be will selection.