Who Gives A Fish Forums

Got a 75 gallon tank with 5 Discus, all around 4 inches. They've been in there for 3 months, but every time I try adding tank mates like Tetras or Corys, they freak out. Water params are good, 0 ammonia, 0 nitrite, nitrate at 10 ppm. Temp's at 84°F, pH 6.5. Using a Fluval canister filter and do 30% water changes twice a week. Why are they so sketchy with other fish?

Discus are naturally shy and territorial, especially in smaller groups. Your tank's size is decent, but they might feel exposed without enough hiding spots. Try adding more driftwood or tall plants like Amazon Swords. Also, Tetras can be nippy, which stresses them out. Corys are usually chill, but if they're darting around, it could spook the Discus. How's your lighting? Bright lights can make them feel vulnerable.

Yo, my Discus were the same way till I added some Cardinal Tetras. They're way less aggressive than Neons. I keep my tank dim with floating plants like Frogbit, and they're way more relaxed now. Also, try feeding them first before adding new fish. If they're busy eating, they won't freak out as much. What's your feeding routine like?

PureAddict wrote: ↑Tue Aug 26, 2025 12:39 pm Yo, my Discus were the same way till I added some Cardinal Tetras. They're way less aggressive than Neons. I keep my tank dim with floating plants like Frogbit, and they're way more relaxed now. Also, try feeding them first before adding new fish. If they're busy eating, they won't freak out as much. What's your feeding routine like?

That's a solid point. Discus are super sensitive to changes, so introducing tank mates during feeding time can help. I'd also recommend quarantining new fish for a couple weeks to avoid introducing diseases. Have you noticed any signs of illness in your Discus?

Mine were the same until I switched to a darker substrate. They're less stressed now, probably 'cause it mimics their natural habitat. I also added some Java Ferns and they love hiding in them. What kind of substrate are you using? If it's too light, it might be part of the problem.

Thanks for the tips, everyone. I'll try adding more plants and dimming the lights. I've got a light sand substrate, so maybe that's part of it. I feed them frozen bloodworms and pellets twice a day. No signs of illness, just skittish behavior. Gonna try the feeding trick next time I add fish.

Sand's fine, but darker substrates do help them feel safer. Also, make sure your new fish are acclimated slowly. Drip acclimation over an hour or two can reduce stress for everyone. How's your water flow? Too much current can make them uneasy.

Yep, slow acclimation is key. I also found that keeping the tank in a low-traffic area helps. If people are constantly walking by, they'll stay stressed. Mine are in a corner of the living room where it's quieter. You notice any difference in their behavior at different times of day?

PureAddict wrote: ↑Tue Aug 26, 2025 7:20 pm Yep, slow acclimation is key. I also found that keeping the tank in a low-traffic area helps. If people are constantly walking by, they'll stay stressed. Mine are in a corner of the living room where it's quieter. You notice any difference in their behavior at different times of day?

Exactly. Discus are super observant. If they're in a high-traffic spot, they'll always be on edge. Mine are most active in the early morning and late evening. Maybe try observing them at different times to see if they're more relaxed when it's quieter.

Another thing to consider is the size of the tank mates. If they're too small, the Discus might see them as food. Too big, and they might feel threatened. I've had luck with Rams as tank mates. They're peaceful and similar in size. Ever tried those?