Who Gives A Fish Forums

My discus fry stopped growing at around 1.5 inches. They've been stuck at this size for weeks. Tank is 55 gallons, water temp at 86°F, pH 6.8, ammonia and nitrite at 0, nitrate under 10ppm. I do 50% water changes every other day, feed them beef heart mix 4 times daily. Filter is a Fluval 307, substrate is bare bottom. Any ideas what's up?

Sounds like you're doing everything right. Maybe check the protein content in your beef heart mix. Some brands skimp on quality. Also, how old are they? Sometimes they hit a plateau before another growth spurt.

I had the same issue last year. Turned out my water was too soft, like below 3 dGH. Added a bit of crushed coral to the filter, and they started growing again. Might be worth testing your hardness if you haven't already.

ailam wrote: ↑Tue Sep 02, 2025 8:47 am I had the same issue last year. Turned out my water was too soft, like below 3 dGH. Added a bit of crushed coral to the filter, and they started growing again. Might be worth testing your hardness if you haven't already.

This is solid advice. Soft water can mess with their mineral uptake. Also, how's their appetite? If they're not eating aggressively, try mixing in some live blackworms to stimulate feeding.

Could be crowding too. How many fry are in the 55? If it's more than 20, they might be stunting each other. I've seen slower growth in overstocked tanks even with perfect params.

Thanks for the tips, everyone. I'll test the hardness today. There's about 15 fry in there, so crowding might not be the issue. Appetite's been decent, but I'll grab some blackworms to see if that kicks things up.

Yep, blackworms usually do the trick. Also, double-check your heater calibration. I've had a sketchy one that was off by a couple degrees, and it made a bigger difference than I expected.

stamps wrote: ↑Tue Sep 02, 2025 9:16 pm Yep, blackworms usually do the trick. Also, double-check your heater calibration. I've had a sketchy one that was off by a couple degrees, and it made a bigger difference than I expected.

Good call. Temp swings can stress them out enough to slow growth. What brand heater are you using, JUSTICE?

If all else fails, consider genetics. Some lines just grow slower. Had a batch from a certain breeder that took forever to hit 3 inches, while others from different stock blew past them.

True, but I'd rule out environment first. JUSTICE, how often are you cleaning the filter? A clogged canister can drop flow, which might not remove waste efficiently even if params look good.