Who Gives A Fish Forums

My discus has developed black spots over the past week. Tank is 75 gallons, temp at 84F, pH 6.8. They're about 4 inches, eating beef heart and flakes daily. Water changes every 3 days, 30%. Sponge filter and canister running. No new tankmates. What's causing this?

Black spots can be stress or water quality. Test for nitrates, might be creeping up. Also, check if they're getting bullied, even if you don't see it. Sponge filter alone might not cut it for bio load in a 75. What's your nitrate reading?

Aw, poor thing! Could it be from the lighting? I had a similar scare when I switched to brighter LEDs. Maybe dim it a bit and see if they chill. How long are your lights on each day?

Yep, sounds like stress vibes. Mine did that when I moved 'em to a new tank. You gotta keep things steady with these guys. Maybe skip a feeding day, let the water settle. What kinda substrate you using?

Or it's just their natural coloring, dude. Some discus get darker when they're happy or dominant. You sure it's not just them flexing? Mine got spots when they claimed their corner. How many you got in there?

Nah, black spots ain't normal if they popped up quick. Could be parasites messing with 'em. You dosing anything lately? Sometimes meds can trigger weird reactions. Check for flashing or clamped fins.

Nitrates are at 10ppm, so not terrible. Substrate is sand, lights on for 8 hours. No flashing, but one does hide more now. Should I try a salt dip or just wait it out?

Sailor wrote: ↑Fri Jul 18, 2025 8:45 am Nitrates are at 10ppm, so not terrible. Substrate is sand, lights on for 8 hours. No flashing, but one does hide more now. Should I try a salt dip or just wait it out?

10ppm is fine, but the hiding's sketchy. Salt dip could stress 'em more. Maybe up the water changes to every other day for a week. How's the flow from your canister?

If they're hiding, maybe dim the lights like I said earlier. Mine stopped hiding when I added floating plants. You got any driftwood or plants to break up the space?

Sand's good, but it can trap gunk. You vacuuming it proper? Might wanna stir it up during water changes. Also, beef heart every day's heavy, maybe mix in some pellets to lighten the load.