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I've got a 75-gallon tank with 8 adult Discus, a school of 12 Cardinal Tetras, and 6 Corydoras. The Discus are around 5-6 inches each. I do 50% water changes twice a week, pH is stable at 6.5, temp at 84°F. They seem fine but I'm worried about space. Am I pushing it?

That sounds like a solid setup, but 8 Discus in a 75 might be tight long-term. They're big swimmers, and stress can creep up. How's their behavior? Any aggression or hiding? I'd watch for signs like clamped fins or lack of appetite.

jolvy wrote: ↑Tue Sep 16, 2025 4:52 pm I've got a 75-gallon tank with 8 adult Discus, a school of 12 Cardinal Tetras, and 6 Corydoras. The Discus are around 5-6 inches each. I do 50% water changes twice a week, pH is stable at 6.5, temp at 84°F. They seem fine but I'm worried about space. Am I pushing it?

Technically, you're at the upper limit. The general rule is 10 gallons per adult Discus, but your water change routine is excellent. If they're not showing stress, you might be okay, but I'd consider upgrading if you notice any issues. Also, keep an eye on nitrates—they can spike faster in a stocked tank.

jolvy wrote: ↑Tue Sep 16, 2025 4:52 pm I've got a 75-gallon tank with 8 adult Discus, a school of 12 Cardinal Tetras, and 6 Corydoras. The Discus are around 5-6 inches each. I do 50% water changes twice a week, pH is stable at 6.5, temp at 84°F. They seem fine but I'm worried about space. Am I pushing it?

Technically, you're at the upper limit. The general rule is 10 gallons per adult Discus, but your water change routine is excellent. If they're not showing stress, you might be okay, but I'd consider upgrading if you notice any issues. Also, keep an eye on nitrates—they can spike faster in a stocked tank.

Yo, that's a packed house! I ran 6 in a 75 and even that felt sketchy. They need room to flex, ya know? If they're chill now, cool, but don't push it. Maybe cut back on the tetras if things get weird.

I've got a similar setup, 7 Discus in an 80-gallon with Rummy Noses. Key is filtration—I run dual canisters and a sponge. If your water's pristine and they're eating like pigs, you're probably fine. But yeah, watch for nipping or lethargy.

Ticgo wrote: ↑Wed Sep 17, 2025 7:07 pm That sounds like a solid setup, but 8 Discus in a 75 might be tight long-term. They're big swimmers, and stress can creep up. How's their behavior? Any aggression or hiding? I'd watch for signs like clamped fins or lack of appetite.

Spot on. Also, Discus are social but need their space. If they start staking out corners or darting, it's a red flag. My crew got moody in a 75, so I upgraded to a 120. Night and day difference.

Your water change routine is commendable, but crowding can still cause subtle stress. Discus secrete hormones that build up, even with clean water. If you can't upgrade, consider adding more plants or driftwood to break sightlines and give them zones. Floating plants like Frogbit can help too.

Man, I'd be sweating with that many big fish in there! My rule is 1 Discus per 15 gallons if you wanna keep it comfy. But hey, if they're vibing and your water's on point, roll with it. Just stay sharp on those water changes.

Man, I'd be sweating with that many big fish in there! My rule is 1 Discus per 15 gallons if you wanna keep it comfy. But hey, if they're vibing and your water's on point, roll with it. Just stay sharp on those water changes.