Thank bro for the share. I fed the same I feed all mine tanks with - small thawed marine bait fish, mostly several herring species, some anchovy, whiting, mullet, etc. Their disease looked suspicious, perhaps you are right about the diet. I will try again surely, if God is willing.Saw that thread, you're a brave man, keeping a tig in a tank with so many rocks.
Very sad that you lost your fire eels after getting them on cut fish. What fish were you feeding them. In my experience some fish meat doesn't bode well, in my case clarius magir meat caused bloat and death of many bichirs, and this was with hardly 4-5 feedings.
The Color doesn't depend on the substrate Color or the brightness of light used in tank, they are not like tire tracks, these can get very bold and very friendly, mine are so aggressive during feeding, they would start pulling on the skin of my hand, if they didn't find the food immediately, they will also come out of the water at the top of I hold food. Not able to find that videoi had put on youtube.