Young discus fins

Hi, I'm new to breading and I'm growing now a few discus from different spawns. I've noticed that the fish have different types of fins. Between the older ones and the younger, so I'm guessing is not a matter of age, maybe slow development regardless of size...

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Attachment 131183

As you can see, one has a short dorsal fin and the other has a "normal" rounded fin.

Is this normal and when they grow they will develop full round fins or do you think think this is a malformation?

Thank you

It could be genetic, environmental or a lack of minerals. I had a similar issue years ago and I added a small amount of calcium chloride - Prestone Driveway Heat (ice melt) and it corrected the problem. Unfortunately, once it develops it cannot be corrected. Mine were culled...

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Yes, that maybe it... I use the same RO water with some calcium and magnesium that I use for the main tank, so not much. TDS around 100. Maybe I bring it up to 150 but I was afraid of messing to much with hardness. I bring it up slowly to 200 or so. Thank you

It may be genetic as Brian already mention, look at the parents finnage. May want to check for low kh readings. You may want to cull as both Discus are far behind in growth. One last note if you notice that all spawns from different pairs have this finnage then it's a water problem.

Cliff

I agree with Cliff that you may want to cull those. Even without the defective dorsal, they are under developed. But it's your choice depending on what your goals are.

I use RO for spawning only. I start adding straight tap water immediately after they hatch and by the time they are free swimming the tank is all tap with a TDS of around 430. Even with this method, I did have this issue and it was with one pair only so I think it was genetic. Possibly in that the genetics didn't allow for normal calcium intake. With the added calcium chloride, the problem went away. Just a theory though...

Thank you everyone, parents look ok, so maybe an hereditary genetic issue but honestly odds are I did something wrong. With hardness for sure and probably something else. I just feel lucky I got so far this early in my discus adventure.

I will not cull them, even if I was willing to do so, at this stage in my journey they serve me more alive as practice for learning than dead. I will for sure not give them away. I do not have room neither so sooner or later some will indeed have to go.

I'm already aging tab water and will increase hardness to 450 TDS progressively during the next few days. I was not consistent with feeding on week days, I'll see what I can do about that now that they are eating granulated food.

I'm impressed with your good sense and fast learning, Onpots. I'm betting on you being around for a long time.

Thank you Liz, I've been in the hobby for 25+ years, just new to discus, I set up my first discus tank a little over a year ago. I've been reading a lot from experts like the ones around here. Still learning, doing some things deliberately my own way and probably making many mistakes... But very happy with how things are going so far.