Reef not consuming Ca?

mtnrunner · Jul 10, 2021

My 90 gal mixed reef that is over 20 years old has me stumped. Normally my Trident doses Alk and Ca as I have scheduled and the tank maintains an average Alk of 9.5 and Ca at 429. Over the past 3 or 4 weeks, my Ca started going high to the point I had to stop dosing any Ca at all. I have not been adding any Ca for about 2 weeks now and the Ca readings continue to hover around 530. Odd.

I have double checked my Trident against Hanna checkers and it agrees with the Ca reading. I have not changed anything else in my tank. My corals appear fine, but not showing strong growing points.

What could be causing my corals to not be consuming Ca?

taricha · Jul 10, 2021

What about your other parameters? Did alk consumption also stop? What about nutrients, nitrate phosphate? Are we seeing a total stop in all consumption or is it only calcium?

Timfish · Jul 10, 2021

Sounds like a case of "Old Tank Syndrome". If the rest of your water parameters are withing "acceptable" levels I'd guess a shift in hte ecosystems equilibrium that doesn't favor corals. There's all kinds of microbial stuff and competition with DOC going on in reef systems (Forest ROhwer's "Coral Reefs in the Microbial Seas" is an excellent introduction). If you're not doing water changes even if you run GAC and skim refractory and hydrophilic DOC will be building up in your system.

If you're not doing water changes I would start doing them. Corals and algae are both dumping DOC in the water and it ends up promoting different types of microbial processes. Doing water changes, besides directly removing DOC also removes both hydrophilic and hydrophobic microbial stuff equally and with repeated water changes should let the stuff promoted by corals gain dominance

Assuming you have a sand bed but aren't running a Jaubert system I would be using a gravel vacume to clean it out carefully and I would also be replaceing at least some of it.

I very rarely hear about pepole using diatom filters any more but it's something one of my mentors 30 years ago would use occasionally. I've found it can be helpfull when dealing with "Old Tank Syndrome". Running a diatom filter a day or two will remove a lot of the microbial stuff that's in the water, again both the hydrophilic stuff and the hydrophobic stuff. The idea is it reduces the microbial load that's detrimental to corals and lets corals promote the stuff that's beneficial to them.

Be patient. Fixing "Old Tank Syndrome" isn't something that happens overnight.

blasterman · Jul 10, 2021

No idea what your mixed reef consists of nor what your previous calcium consumption was.

If you were legitimately dosing calcium before look for a PH drop or probe error.

DrZoidburg · Jul 11, 2021

What is the rest of the filtration setup? Also are you doing anything like auto water change?

arking_mark · Jul 11, 2021

1st I'd triple check my Ca testing as it's prone to errors and is usually pretty inaccurate.

However assuming your measurements are good, the only process I'm aware of that doesn't use Ca and Alk together is the Nitrogen cycle.

So if you coral growth and abiotic precipitation has stalled and your consuming Alk but not Ca, I'd start checking you nitrate levels.