You have to realize it is INCREDIBLY daunting for the average fish keeper to think about doing this. I'll freely admit, I don't have the nads to try this.
I get it. It is very time consuming too and not inexpensive.
But having done this for years with sharks, with both rigid and semirigid tubes I thought the transition to smaller fish might be possible. When I researched it, I initially found an old post in a news group of someone tube feeding an american eel and a video of someone sticking a turkey baster full of food into the stomach of a lionfish. I thought maybe.
I first chose the clownfish, a hardy, captive raised, inexpensive fish that was already eating. I then decided on the angio catheter because they are hollow, flexible, soft, rounded and come in many sizes. If they were soft enough to insert into a vein, then I figured that they could be inserted into the stomachs fish that sometimes eat hard crustaceans, bristle worms, fins, and other abrasive matter.
In the past, especially with toothed sharks, I lubricated the rigid tube with Pam cooking spray. With the Stat, it is very oily and allows the catheter to slide in.
As for injury, it can definitely happen. I believe I injured and killed my short tail nurse shark pup. I had to hatch it myself and it was terribly thin and weak. I kept it alive for a while with the feeds, but I think I did puncture its esophagus or stomach during the last feeding. I didn't sedate it and it acted injured immediately after the feeding. Dead in the AM.
I purchased the regal because the price was incredible, probably because it wasn't eating, and figured I would give it a go. For most, they should probably leave a fish like that in the store.
I think that using this technique could be very helpful for the store owner with valuable livestock or the person interested in very expensive, rare, and or notoriously difficult fish.