I thought that too for a good while. Dream fish are still a mystery and I think any research is still coming up empty. I think it was Johnathan Ott (?) that speculated 5-Bromo-DMT but don't quote me. I have a few of his books I have not read in a while. I thought I heard that too. But I recently went into my book collection and pulled out a few. Ayahuasca Analogues and Pharmacotheon: Entheogenic Drugs, Their Plant Sources, and History. I guess I technically should have scoured any info before posting but I am impatient.
Still need more info in 5-Bromo-DMT. But I think the effects are separate from what we thought the dream fish could contain. I am not even sure there is a correct species that we know.
But I do think it is known that 5-Bromo-DMT was found in a sponge. Some Smenospongia sponges.