Pics of the fish would help, velvet looks like really tiny particles of gold dust, on smaller fish it will affect the gills, often you can't see the tiny gold dusting on fry.
This is something I encounter with fry from time to time, and as a preventative in my breeding setup medicate accordingly. Mardel CopperSafe will take care of it. Use a med tank with this med, copper will concentrate in & kill algae, releasing the copper back into the water. Algae eating fish will OD on the copper from eating the algae. As long as it is a clean tank, this is a safe medication. I dose fry tanks at half the dosage for the first week, this is something learned from years of breeding, not something your average aquarist wants to get in the habit of doing.
Do not put salt in a tank with catfish, this will irritate them, being scaleless fish. Very few freshwater fish need salt, and it is needed as a medication in very few cases. There is much documentation on this site to that effect.
80F is too warm for your fish, and bacteria multiply faster in warmer water. It will not shorten the life cycle of bacteria, though with ick it will quicken the life cycle, thus the cure.
If you remove your filter media you will be doing 50% water changes daily, and if you don't have another tank to run the media in your nitrifying bacteria will die, and the tank will have to go through cycling. I would remove any carbon if you are medicating with copper, I med tanks with it leaving the media in & have no problems at all. These are heavily stocked tanks, any problems with the bio filtration would show up within 24 hours.
As long as you have adequate water circulation it doesn't matter what position your heaters are in. I have tanks where they are horizontal, vertical, and diagonal, in many cases just tossed in the tank, if they are submerged they are fine. I'm running Ebo-Jagers, VisiTherms, and a couple oddball submersibles, they all work the same.
I certainly don't want to sound as if I'm shooting anyone down, but when I see a med that doesn't have a proven track record, salt being added that will have more of a negative effect than positive, and misinformation on how heaters function I feel I do have to speak up.