Why do the tips burn?

[warriorcookie]

While buying some corals from another member here (thanks again btw), we discussed lower Alk levels being required in low nutrient systems. We briefly pondered the mechanism that causes burnt tips on SPS that so many are familiar with when Alk rises too high and nutrients are close to zero.

Anywho... I stumbled across this article at Advanced Aquarist where they measured the rate of photosynthesis and growth at various levels of Alkalinity. The cause of burnt tips is speculated at the very end. For those that like to nerd out, enjoy! How to Grow Corals Quicker: Effects of Various Alkalinity Concentrations on Rates of Zooxanthellae Photosynthesis (http://www.advancedaquarist.com/2016/9/aafeature)

[Myka]

Another speculation is that increased alkalinity causes the coral the lay down skeleton quicker, and the skin cannot develop as quickly due to the low nutrients, so essentially the skeleton bursts out the end. People come to this conclusion from seeing pale tips in Acros that are growing quickly. I'm not sure I buy this theory. My Acros will get tip burn if alk hits about 8.5 dKH, so according to this theory, my Acros get a sudden growth spurt for like 2 days??? I don't know, I don't buy it. Plus, you will see alk burn on Acros that have dark skin which indicates that the Acros is getting lots of nutrients (even if the water column nutrients are low).

[FishyFishy!]

In my personal experiences its from alk swings.

[Animal-Chin]

I've carbondosed twice and each time when I started my alk was at 9 and my acro tips burned. I find that as soon as you add a carbon source you have to get your alk below 8 or burning happens. I think it has something to do with how carbon and alk react. My nutrients didn't drop so fast that the tips burned, my nitrate was still high when the burning occured. I drop my alk under 8 and everything evens out and the burning stops.

[warriorcookie]

Ya, that's been my experience too, as Alk rises too much higher than 8.5ish the tips burn. This wasn't about what causes it, but more so the mechanism of action.

Far from fact, but interesting to speculate.

[Reef-Geek]

I am running out of AF reef salt and going back to IO, AF's dKH is about 8 and IO's is about 10. Should I be concerned with tip burning? How do people with IO and ULNS prevent tip burning, I don't want to work with muratic acid unless I have to.

[FishyFishy!]

I am running out of AF reef salt and going back to IO, AF's dKH is about 8 and IO's is about 10. Should I be concerned with tip burning? How do people with IO and ULNS prevent tip burning, I don't want to work with muratic acid unless I have to.

Could you find coralife salt? Mine is usually around 8 - 8.4 when mixing new water.