Red gills are fine on Cherry Barbs, they are red fish. I took a peek at mine and their entire body is red - including the gills. Now if they are a significantly different color of red than the rest of the body I would wonder, but Nitrates at a level of 40 ppm are hardly likely to do any damage. The 180 ppm is.
With my first tank, I had read about cycling with food so I gave it a try - all I got was ridiculously high Nitrates. I switched to ammonia (pure not any with detergents in it) and I had tanks with zero nitrates (along with zero ammonia and zero nitrites. I always wondered why one would cycle with food - because there is no bacteria to convert nitrates to ANYTHING except dirty water. Only water changes can get rid of Nitrates. So try to get rid of the nitrates with a 95% water change, then test all parameters for a couple of days (without adding any food) and see if you continue to get zero ammonia and nitrites and Nitrates at a level of 10-20. Make sure you clean your gravel if it shows lays of food on it or in it - and clean it deeply to get rid of all the decomposing food, unfortunately that may kill your cycling.
If you ever cycle an aquarium again please use ammonia - it's about $1.50 in the grocery store, just be sure to read the ingredients to make sure they haven't added perfumes or detergents - if they have, then keep looking for pure ammonia - perhaps a hardware store would carry it. I had multiple choices at my grocery store so I had no problem finding a pure form. If you lose all your cycling after the big water changes (and hopefully you won't) then start over with Ammonia rather than food. Then once you are cycled, you will STILL show a relatively high volume of Nitrates (they have nowhere to go) but if they are semi-reasonable, the do a 75% water change. Then add a small amount of ammonia - if you tank is cycled, the ammonia should disappear overnight but may show up as a low level of nitrates. If you get two days in a row where the tank is adequately cycling the ammonia then you can do one more water change and add your fish. (Nitrates do not have to be zero to consider your tank cycled, just make sure they are 20 or less ppm. If it's higher then do a water change and you can probably still add your fish since you'll be doing water changes weekly for the rest of your natural life LOL. I spend my time doing the dreaded water changes by talking to my fish, commenting on a brighter color or just that they are so beautiful, I give them a special treat like dried tubiflex worms which many fish love. I have one so-called Herbivour and I spent good money getting him a proper diet - which he totally ignores and is now eating all the carnivors food - so I give him a little lecture every day (I actually feed him first, trying to get him to eat his special diet - which he just ignores (it does smell awful) but while his selected diet may shorten his life, at least it will be a happy little life. I also spend my time examining every fish in the tank for abnormaliies.
Best of luck and Happy Holidays!
