M.digitata periodically unhappy??

[plankton]

This is for SPS experts. I have a one year old 25G lagoon tank, corals are growing, great color but about once per month my 8” digi colony polyps will partially contract and color off then recover and repeats!!

Whats the deal? Just did 4G water change in case there is something weird going on but otherwise tank chem is within parameters.

Any idea?

salinity 1.025, phosphate 0.16, alk 8.9

 

[Unregistered1]

your mag looks a little low. temp??

 

[plankton]

Yeah mag a bit low and was about to add some mag to raise to 1350. Temp is 77’ish

 

[blasterman]

Digis tend to like higher nutrient levels and the problem might be the water change.

I have the same problem in my 20L that is almost wall to wall montipora. If I do a water change I lose some color because of the nutrient export. This is just part of the grief with small tanks. Not enough volume to buffer nutrients when water is changed. Reds and oranges in my experience like 'spicy' water and dont handle phosphate dives. Same with a lot of birdsnests.

Unless you really need to export nitrate just back off water changes.

 

[plankton]

At one point my phosphates where 0.01 and m.digitata was super stressed to I stopped carbon dosing and started feeding tank twice as week and now phosphates at 0.16 So, I guess the increase in phosphates also stressed the digi. <sigh>