Help me out - polyp extension conundrum

[matthewduren]

I have a relatively new 40g tank (6 mo), and some of my SPS is not seeing great polyp extension. Alk 9.1, Calcium 490, mg 1520 (a bit higher than I'd like...reef crystals out of the box mixes to 1700+), ph 8.2, nitrates and phosphates undetectable per 2 different LFS. I do not run carbon or gfo, I do weekly 5-10g water changes, I dose kalk in my ATO and supplement with two-part on saturdays if necessary (been pretty stable 8.5-9.0). I have a fuge with chaeto that runs about 15 hours 10p-1p (have not trimmed the chaeto, it's not huge).


The PE issue is affecting both of my acros and some montis (spongodes, stellata, and setosa, but not ff digi nor some other unknown branching/encrusting monti)...birdsnest, stylo, and psammocora unaffected.


BASED on all of this info, my best guess is that my NO3 and PO4 are too low, along with slightly high alk. I started feeding reef roids daily on Monday, and increased feeding in general, but have not seen much improvement in PE. I have not seen any pests (AEFW, nudis, redbugs, etc), but I'm not ruling out redbugs.


I'm open to suggestions and willing to provide whatever other information you may need.

 

[Scarface8]

In my own experiences, PE happens more when the corals are hungry, if you think about it, we open our mouths to put food in there , my guess would be that no3 and po4 are higher than the lfs is detecting, get your own test kits and test it out for yourself, po4 I'd recommend Hanna hi713 and no3 I'd say salifert or Red Sea, do your water parameters fluctuate much? Alk is a touch high, something you didn't mention was what fish you have in there, got any fish that may be nipping at the corals? What's the pe like at night about an hour or 2 after lights go out?

 

[matthewduren]

Fish 2 clowns, 2 halichoeres wrasses (melanurus and yellow), and an assessor basslet. The wrasses pick at stuff all day but I've never seen them pay any attention to the corals. PE after the lights go out (so, wrasses under the sand) is about the same as it is during the day or less.


I've tested nitrate on my own with the red sea test and I've also found it to be undetectable. I don't have a phosphate test kit but I may end up getting the hanna checker...hate paying $50 bucks for something I'll use once a month. Very little algae in this tank...the fuge has chaeto and a little bit of hair algae that I clean off the glass once per week. The nozzle on the return has a bit of hair algae. No other algae at all.


I also added some carbon this afternoon (just in a bag) in case there is something funky in there. Parameters are pretty stable, the kalkwasser in my ATO does a good job with that (it's on a DIY float switch with a timer for backup...can run 1 minute every 20 minutes). pH always between 8.1-8.3 even at night. So I'm definitely stumped.

 

[aznsnakeboy89]

This might not be true but it works for me so i will throw it out there. "Flow" I had the same frustration about the PE before when i had my 2 mp10 place in the back of the tank. Ever since i moved them side by side i get great PE and noticeable grow.