Help please, tetra flashing

Ok so my tetras have been in the 20 long for 2-3 days (used substrate and 60 gallonsponge filter from my cycled 10 gallon tank, established for 1 year), I introduced IAL to the tank yesterday and I noticed that one of the larger tetras is flashing consistently (5/6 times while I watched) on the IAL on the bottom of the tank do you think it’s from stress or sickness. I boiled the leaves before adding and let them cool back down. The other new additions are baby mystery snails the night after the fish were added to the 20 gallon long (they just hatched and they’re in a breeder box). I’ve included pictures of the tetra that’s flashing (larger one at the front of each image). His colors have gotten better not worse since I bought him and I don’t see any white spots.
Water parameters~
pH: 7.0
Nitrites: 0ppm
Nitrates: 0ppm
Ammonia: 0ppm

 

The new additions might have parasites in the gills. If possible up the temp to 86 degrees & keep it there for 10 days. See if that helps.

 

They look awfully pale. Is the lighting that bright all the time?
Flashing does not always mean ich, sometimes not even sickness. If disease it could also be gillflukes, sometimes it's just some particles floating in the water getting in the gills. Fish do not just scratch when there is a parasite.
I often see my cardinals flash 2-3 times a day and then not at all for weeks. And I know there are no parasites in my tank anymore.

 

They look awfully pale. Is the lighting that bright all the time?
Flashing does not always mean ich, sometimes not even sickness. If disease it could also be gillflukes, sometimes it's just some particles floating in the water getting in the gills. Fish do not just scratch when there is a parasite.
I often see my cardinals flash 2-3 times a day and then not at all for weeks. And I know there are no parasites in my tank anymore.

The lighting is from my lamp, I keep that on during their “day” hours, I’m trying to growout duckweed and I’m thinking about getting other floating plants as well since my mystery’s have been eating the duckweed. I had 6 younger glowlights and got 2 older glowlights a few days ago the older larger glowlights had actually shocked me when I looked at them at home because they were almost white (even asked fishlore if they were actually glowlights). They’ve been more active since they’ve been in the 20 gallon and they are slightly darker now but not by much.

The new additions might have parasites in the gills. If possible up the temp to 86 degrees & keep it there for 10 days. See if that helps.

Would this have any other visible signs? The tetras gills look fine, or is flashing the only visible sign?

 

Raising the temp is just a non toxic, non med method of combating a potential, yet unseen Ick infection.
Ick infestations often start in the gills and are not visible on the body & fins until days later. The elevated heat is just a precaution.

 

Raising the temp is just a non toxic, non med method of combating a potential, yet unseen Ick infection.
Ick infestations often start in the gills and are not visible on the body & fins until days later. The elevated heat is just a precaution.

Ok, just set my heater.

 

Yes. It will gradually warm the tank & won't stress out the fish.