From the single photo provided I dont see ich. Would need a full body shot. Yes bulging eyes are a normal Oscar thing. What I do see is a fish that has been, or maybe still is, living in water that is less than ideal. The cratering, general roughness on and about the forehead. Possible scars from past bouts of hith. First and foremost is always clean water. Whatever it takes to make his tank water have a consistent nitrate level of under 10ppm. If thats a 2-3x weekly 75% water change, then thats what you need to do. No such thing as too much clean water for an Oscar. They are a tough cichlid, but iffy water quality hits them hard.
I'm not getting what you're saying is cratering. Doesn't look any different than other oscar pics I see online. Are you talking about the sensory pits??
Water conditions are fine. Ammonia, nitrites, nitrate.
NO3 I've never seen higher than 20, usually at 10 or less.
NO2 I've never seen change from white on test strips, 2 brands.
PH has gotten low once, down to around 6.2. It's usually right at 7.0.
Test strips are notoriously inaccurate. Unless this is a single fish in 250 gallons, I respectfully suggest that there is no way to have safe nitrate with a twice monthly water change. No, not sensory pits or nostrils. The roughness I see is the entire forehead area. The Oscar is sometimes referred to as the Velvet Cichlid, named from the super smooth flesh on its head. A little info please.. size of tank, filtration, tank temperature and general size and age of the fish. Any tankmates? Whats it usually eat?
I've had it for 4 months now. Was about 3.5" when I got it, 7.5" now. 65 gallon tank currently, getting a 125 soon.
Only tank mates now are a male and female BN pleco. Had a Jack Dempsey and a Parrot Cichlid up until a month ago, put them up for adoption because they all started fighting.
Eats 1 small frozen/thawed peeled shrimp cut into chunks per day, as well as Hikari Gold floating Cichlid pellets (medium).
Filtration is a Top Fin 400gph hang on back with just a thick sponge inside, and a Cobalt EXT canister 210gph with coarse sponge, carbon, bio rings, and floss. Also have a Green Killing Machine UV sterilizer.
Thx for the detailed info. You have a pretty good setup, and the 125 upgrade will be most welcomed. I suggest you invest in a liquid water test kit. API freshwater kit is widely used and most trusted. Your Oscar is surely living in high nitrate water. To remedy that, more frequent and higher volume water changes. Go with 75% every 5 days or so. Remove the carbon from the canister, it does more harm than good. Hikari is a decent food, but fish will do better with a more varied diet. Try some fruit pieces. Get a good amount of veg content into him. Oscars do well with a veg based pellet, or even kelp wafers that plecos and other bottom feeders like. Freeze drieds like krill, shrimp bloodworm, tubifex worms. Live crickets and earthworms when available. NEVER feeder fish. As Oscar is a big waste producer, a thorough substrate vac at each water change is a must. Temp is a bit low. I find Oscars do best in water of at least 80, and still very comfortable at 86. Raise a couple degrees per day. When you move up to a 125, more filtration will be needed. Look into a Fluval FX6. Once an Oscar contracts hith, or lle, or even enters pre stages of either, the chances of recurrence are greater. You need to clean his water up as priority one, keep it pristine going forward