Sorry, been running about with family events and school. Didn't have a chance to see this post among the posts.
Other than the soft gel's may not be so soft as you think and all the goodies may be going to waste. Digestive tract and absorption of said soft gel's into the said fish may be a time constraint issue.
The other thing with Omega 3's is that if they get over a certain temperature, they are no good any more. IIRC it is somewhere in the 80F range. When my dog had cancer, I was trying to source some guaranteed fresh, if you will, Omega 3 fish oil. Closest I got was a local pet shop that kept it refrigerated. Boy, does that stuff stink! And it don't wash out of clothing either!
JKB is smacked dead on this one. Soft gel requires time to dissolve, not at 80°, but actually at 97° in a liquid environment in X hours, based on the studies done by the nutritionists panel when they designed various gel type for the pharmaceutical grade capsules. The gel was designed to break down rapidly in high temp environment with certain acid concentration, such as your stomach, but to retain their structural shape in various humid storage and shipment environment. Once acid is introduced, it will only take less than 2 minutes to fully dissolve. The fish's stomach doesn't have the high volume of acid to break the capsule size designed for human. However, the holding time inside the fish stomach to digest is very long, at high low concentrated pH. Unfortunately, the temperature factor also now come into play. Once again, the gel designed for human's stomach, not pets nor fish, at high temp, and low pH exposure.
As for the concentrated fish oil, nothing wrong with that. It's fish oil extract for human consumption. The oil gone through quite a bit of processing, removing the essential "raw" lipids and amino acids that are needed by the fish. As human, we cook our fish, and only benefit about 25% of the amino acids and lipids derived from the cooked fish. This is why Japanese love their raw fish. For pets and fish, the reason why the fish oil required refrigeration is because oil is in its near "raw" form (85% after processing). That's why it stinks to high heaven. Have you ever think of incorporating flax seed oil instead? Less mess, same concentration, no stench.
...and it's anchovy!
My equation goes something like this:
6-inch FEEDER BLUEGILL + 3 SOFTGEL TABS OF OMEGA-3 = RAINBOW TROUT
...and with a simple hemostat, the softgel tabs go down real easy.
Buying dried anchovie and mixed together with dried krill/shrimps, along with dried seaweed, and make them into pellets, would be the best ideal to promote heart healthy amino acids and lipids for fish's diets. Wish I have the pellet's making machine to incorporate it all for you. Alas, having a family and doing experiments can be counter productive, especially living in California.