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My Acropora frags have been in the tank for three months but aren't showing much growth. I've got a 75-gallon tank with T5 lighting, running at 8 hours daily. Parameters are stable, 8.1 pH, 1.025 salinity, 0 phosphate. Any tips to kickstart growth?

Acros can be picky. What's your alk and calcium sitting at? I've found keeping alk around 8-9 dKH and calcium at 420-450 ppm works best. Also, how's your flow? They need random, turbulent movement to thrive.

I had the same issue until I bumped up my feeding. Try dosing amino acids or reef roids a couple times a week. My Acros started coloring up and extending polyps within a month.

Yep, flow and food are key. I run two MP40s on opposite sides of my 120-gallon, and my Acros are finally taking off. Also, check your magnesium levels. Low mag can stunt growth big time.

Lighting duration might be too short. I run my Radions for 10 hours with a gradual ramp-up. Acros need that extended peak period to photosynthesize efficiently.

Veloric9 wrote: ↑Mon May 19, 2025 7:29 pm Acros can be picky. What's your alk and calcium sitting at? I've found keeping alk around 8-9 dKH and calcium at 420-450 ppm works best. Also, how's your flow? They need random, turbulent movement to thrive.

My alk is at 7.5 dKH, calcium at 400 ppm. Flow is two Nero 5s on random mode. Maybe I need to tweak the alk higher?

7.5 dKH is on the low side for Acros. Try raising it slowly to 8.5. Also, check your nitrate levels. A little nitrate (5-10 ppm) can actually help with growth, contrary to old-school thinking.

kaylder wrote: ↑Mon May 19, 2025 10:01 pm Yep, flow and food are key. I run two MP40s on opposite sides of my 120-gallon, and my Acros are finally taking off. Also, check your magnesium levels. Low mag can stunt growth big time.

Totally agree on mag. Mine was at 1200 ppm, and things were sluggish. Bumped it to 1350, and growth exploded.

Another thing to consider is trace elements. I started dosing a trace element blend, and my Acros responded really well. Just don't overdo it. Small, consistent doses are the way to go.

Have you tested your potassium levels? Low potassium can cause Acros to stall. I aim for 380-400 ppm. Also, make sure your T5 bulbs aren't too old. They lose intensity after about 9-12 months.