Who Gives A Fish Forums

I've got a 75-gallon tank that's 24 inches deep. My Discus seem stressed, and I'm wondering if the depth is the issue. They're about 4 inches long, and I do weekly 50% water changes with RO water. Tankmates are just a few Cardinal Tetras. Filter is a Fluval 407, temp at 84°F. Substrate is sand with a few driftwood pieces. Feeding them frozen bloodworms and pellets twice a day. Anyone else deal with this?

Depth isn't usually the problem unless it's over 24 inches. More likely it's water quality or tankmates. What's your nitrate level? Discus prefer shallow tanks, but 24 inches should be fine if everything else is stable. How long have they been in this tank? Any recent changes to lighting or filtration?

Nitrates are around 10 ppm, and they've been in this tank for about 3 months. Lighting is a Fluval Plant 3.0, on for 8 hours a day. No recent changes except adding the Cardinals 2 weeks ago. They're not aggressive, but the Discus started hiding more since then.

BlondeBloom wrote: ↑Wed Jul 30, 2025 2:23 pm Nitrates are around 10 ppm, and they've been in this tank for about 3 months. Lighting is a Fluval Plant 3.0, on for 8 hours a day. No recent changes except adding the Cardinals 2 weeks ago. They're not aggressive, but the Discus started hiding more since then.

Cardinals might be the issue. Even if they're not aggressive, Discus can be shy with new tankmates. Try dimming the lights or adding more hiding spots. Also, check if the Cardinals are competing for food during feeding time.

I've kept Discus in a 30-inch-deep tank with no issues, but they were adults. Yours are still juveniles, right? They might feel exposed in a deeper tank. Try floating some plants to break up the light and give them cover. Also, how's the flow from your filter? Too much current can stress them out.

yo, my discus were sketchy too when i added tetras. took em a minute to chill. maybe cut the light time to 6 hours? also, beef heart mix got mine way more active. just sayin.

melodic wrote: ↑Wed Jul 30, 2025 6:00 pm yo, my discus were sketchy too when i added tetras. took em a minute to chill. maybe cut the light time to 6 hours? also, beef heart mix got mine way more active. just sayin.

Reducing light time is a good idea. Discus are sensitive to bright light, especially in deeper tanks. Have you tried feeding at the same time every day? Consistency helps them feel secure.

I'd double-check the water params just to be safe. Sometimes RO water can lack minerals if you're not remineralizing it. Also, how's the temp stability? Fluctuations can freak them out. My Discus hated it when my heater was acting up.

Mine were weird at first too, but they got used to it. Maybe give it time? Also, try feeding closer to the bottom. My Discus are lazy and don't like swimming up too far for food.

Could be the Cardinals. Even if they're peaceful, Discus are divas. Maybe move the Cardinals to another tank for a week and see if the Discus perk up.