Why is my coral turning white?

[dorvain]

Noticed my Zoanthids are turning white over the past week. Tank's a 40-gallon with T5 lighting, params are 0 ammonia, 0 nitrite, 5 nitrate. Salinity's at 1.025, temp 78.5. Been feeding Reef Roids twice a week. Any ideas what's up?

[blazekid]

Sounds like bleaching, dude. Check your light intensity, maybe dial it back a bit. How old are your bulbs? T5s lose punch after 9–12 months. Also, what's your alk at? Low alkalinity can mess with their vibe.

[onfire9]

Sounds like bleaching, dude. Check your light intensity, maybe dial it back a bit. How old are your bulbs? T5s lose punch after 9–12 months. Also, what's your alk at? Low alkalinity can mess with their vibe.

Yep, alk's huge. If it's below 7 dKH, they'll stress. Test it ASAP. Also, any recent temp swings? Even a couple degrees can trigger bleaching.

[galenys]

Could be pests too. You dip new frags? Flatworms or nudis might be snacking on them. Grab a magnifier and check for tiny hitchhikers. If it's pests, a quick CoralRX dip might cut it.

[dorvain]

Thanks for the tips, everyone. Bulbs are about 10 months old, alk's at 6.5 dKH. Gonna test for pests tonight and maybe grab new bulbs tomorrow.

[dawnings]

6.5 dKH's sketchy for Zoas. Bump it slowly to 8–9 with a good alk supplement. And yeah, T5s fade fast. Swap 'em out and see if they color back up in a week or two.

[inquiro_9]

6.5 dKH's sketchy for Zoas. Bump it slowly to 8–9 with a good alk supplement. And yeah, T5s fade fast. Swap 'em out and see if they color back up in a week or two.

Totally agree! Stability's key. If you're dosing alk, go slow—like 0.5 dKH per day max. And maybe throw in some amino acids to help them recover.

[flute]

Had this happen with my Acros last year. Turned out my RO filter was shot, TDS was 15. Check your water source if all else fails.

[blazekid]

Had this happen with my Acros last year. Turned out my RO filter was shot, TDS was 15. Check your water source if all else fails.

Good call. High TDS can sneak up on you. If your DI resin's exhausted, it'll dump silicates and other junk into the tank. Test your RODI water before chasing other fixes.