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Delphinus
11-01-2011, 04:56 PM
What are things to look for if you find that Alk suddenly stops depleting at the rate it was going at for a while?

In the last two weeks my Alk stopped depleting. I would dial back the doser but I ended up taking it all the way offline about 5 days ago and even with no dosing the Alk is only dropping about 5ppm per day (it got as high as 200ppm or 11dKH, whereas normally I target it around 140ppm, or about 8.0dKH).

Calcium is still being dosed and sits around 370.

Magnesium sits around 1450 currently.

I didn't think to test tank pH last night but it occurs to me now maybe I should. Seems to me something is up. I'm not sure what to look for here. Any thoughts?

FWIW nitrate is unreadable on the test kits I have, and phosphate tests out around 15-30 ppb on the Hanna handheld (so around 0.015 - 0.03 ppm). I don't know if that's a high value or not. Honestly I would have expected it to be zero as I run zeovit but I'm starting to understand that I actually understand next to nothing, these days :lol:

reefwars
11-01-2011, 05:07 PM
I didn't think to test tank pH last night but it occurs to me now maybe I should. Seems to me something is up. I'm not sure what to look for here. Any thoughts?

:lol:


ph could be something to conside...are you running a hrv in yor house?? if not could be the sudden change in weather we just got and not as much fresh air entering the house.

other than that i have no idea unless something changed in the way of salt batch or something?? idk :)

reefwars
11-01-2011, 05:12 PM
any difference in your corals you notice??

lastlight
11-01-2011, 05:30 PM
You're confident you weren't dosing more than you thought?

Money pit
11-01-2011, 05:38 PM
According to RHF in this article
http://reefkeeping.com/issues/2004-05/rhf/index.php
Your Po4 is fine.

TimT
11-01-2011, 06:29 PM
Alkalinity depletion is a sign of growth so I think it safe to assume that the growth has stopped or been greatly reduced. Some thing has either disrupted it or a nutrient is so low that it is limiting it.

I have found that temperature fluctuations(~3+°f) will cause a disruption.

pH out of range of 7.8-8.4 can have an effect.

Have you tested your water for copper? As RO membranes age they begin to pass more copper. Some houses still have copper pipes.

What is your salinity and has it changed recently?

Your Ca seems a bit low. I would recommend at least 400ppm.

When was the last water change? Was the salt mixed to redistribute the chemicals before being added to the water? Have you switched salt brands recently?

SPS do rely on zoozanthellae for energy and the zoozanthellae rely on nitrate for food. Having 0 nitrate could be a limiting factor.

Just some ideas.

Cheers,
Tim

ScubaSteve
11-01-2011, 06:39 PM
I'm with Tim on these and agree that it's likely a limiting nutrient, temperature or pH that is causing this. I find that my alk depletion rates drop like a rock if pH stays below 8 for any considerable amount of time (like it has recently). With the doors and windows being closed now, watch your temperature and pH.

Now, if you are using ULNS this could be the cause for sure. Try loosening up on your regime for a bit. You may find the system still stays at zero for N/P after doing this, it just means the corals are taking up a bit more of the nutrients and aren't having to compete with the bacterial colonies as much.

Delphinus
11-01-2011, 06:51 PM
The hair algae and small patches of cyano in the tank tell me that nitrate is likely not exactly zero, despite the lack of a colour formation in the test kit (last tested using Elos). I had a nitrate meter at one point but the probes only last about a year and I haven't ponied up the $200 to replace it again (I replaced it once already .. I can't seem to pull the trigger on ordering a replacement).

There is an HRV in the house, temperature seems to remain steady at 26c, salinity is targetted to be maintained at 1.025 although maintaining the magnesium seems to push SG upwards to 1.026 lately .. I don't know if I should lower it to compensate or not. I've just been using IO for salt this year.

Copper, I didn't think of that, but seems prudent to rule it out or confirm if that is indeed the case.

I can't rule out that I might have simply overdosed, what is weird is that up until two weeks ago it was dropping and I was needing to increase the dosing schedule. It does make me wonder if I've simply let the see-saw out of balance with the Calcium being too low. Usually the rookie mistake is testing Calcium and thinking "everything is fine" but letting Alk get too low, maybe I've done the opposite and gotten tracked Alk too obsessively while getting too lax on Calcium.

I can up the Calcium dosing and see how things go. "Back in the day" I always kept my targets at 4.0meq/l (or 11ish dKH) and 400 ppm Ca, I liked how the one number was just the other number with the decimal point moved twice, it was an easy way to remember if the two params were in balance with each other, but I find the whole zeovit/Korallen-Zucht prescriptions to back away from higher numbers and it makes my head swim at times. Polyp extension and colours are great under this system, growth just isn't there in my opinion when I see what other tanks are capable of in a 6 or 12 month period, mine just isn't there.

Plus the hair algae over the rocks .. It seems as if the rock has nutrients bound within (it was all dry rock to begin with, and this particular tank is only about 10 months in so it's possible it simply hasn't matured enough yet).