Interesting Case

[PoonTang]

Yes i would say that he is at the point of the "viscous cycle". His tank sounds about the same as mine but my corals are probably larger and my demand may be higher. The only thing i dose is Kalkwasser and never have to add any 2 part except i will tweek the levels every month or so but never by all that much. I wouldnt worry about the ph at all mine sits around 8.0 and if i try to move it higher (such as in my battle with dinos) it just falls back within a couple of hours. Its a no win battle. Cal and alk are a funny thing as we all know, they work fine when they are all balanced but if you get 1 out of wack then it has the opposite effect on the other. This is partly why i prefer the Kalk route, as it is basically balanced to start with. I would check his mag too. I havnt had to clean a pump from calcification in a year and a half and some of the pumps have never been cleaned.

[Red Coral Aquariums]

Originally Posted by Delphinus

My guess is low magnesium. Before I would track magnesium, I noticed calcium buildup on many of my pump's magnets and shafts. Powerheads .. skimmer pumps .. etc. Calcium precipitates easily when Mg is low. This effect has been profoundly reduced since keepng Mg where it should be. Now I still notice some buildup on the Tunze magnets but nothing that needs to be removed more than say once every 6 months or so.

I have seen this before. Interested to see the mg levels.
Kevin

[sphelps]

Originally Posted by Delphinus

My guess is low magnesium. Before I would track magnesium, I noticed calcium buildup on many of my pump's magnets and shafts. Powerheads .. skimmer pumps .. etc. Calcium precipitates easily when Mg is low. This effect has been profoundly reduced since keepng Mg where it should be. Now I still notice some buildup on the Tunze magnets but nothing that needs to be removed more than say once every 6 months or so.

He doses magnesium weekly to maintain it at 1500

[sphelps]

Originally Posted by Lance

Does the sump chamber where he doses have fairly low flow, or is he dosing the calcium and alk too soon to each other? I had the same problem for awhile in the 90g, (though not as extreme). I use the same recipe, and found if I dose the calcium and the alk into the same chamber I have to make sure there is at least 6 hours between the dosing times or I get calcification. In fact the water in that chamber was even a little milky from the two reacting together. I eventually moved the calcium dosing line to a different part of the sump that has more flow and that helped a lot. Within days after doing this the volume of calcium and alk I needed to dose to keep parameters in line dropped considerably.

Not super low flow, it's a decent size sump but the mag 1800 is running at full open so the sump turn over rate is pretty high. The alk is being dosed automatically along with the kalk top off but calcium is added manually each day. I believe the full 400ml is added at all at once which could be an issue.

[sphelps]

Originally Posted by asylumdown

This sounds exactly like what was happening to me when my water chemistry went weird.

a) what alk supplement is he using? is it baking soda from a grocery store, or something prepared specially for reef tanks? I know they're supposed to be essentially the same, but when I used baking soda, my water chemistry went haywire, and the ratios of solution made no sense. I also ended up with pumps failing weekly due to precipitation.

b) is he adding carbonate or bicarbonate as his alk source (carbonate would be if he's 'cooking' his bicarbonate)? With pH levels and dosing volumes both being that high, I suspect he's adding something with a lot of carbonate, which is considerably less soluble and more likely to precipitate out than bicarbonate.

c) It sounds like he's adding so much carbonate/bicarbonate that his levels are never balanced. Is he using an auto-doser? If he's pushing one past the 'limit', addition of the other will instantly react and precipitate out. I think you can get in to a vicious cycle. I bet at one point in the past he overdosed on one additive (likely alk), which caused a precipitation reaction that depressed his levels of calcium. On a test kit, it would have looked like he had low calcium and normal alkalinity. If he's using a doser, he would have then upped the amount of calcium he was adding every day. However, there would still be excess carbonate being added, so the precipitation would continue, and appear to depress his alk levels. So then he upped the amount he dosed alk, which would depress the calcium levels again... so on and so forth, always upping one, seeing a drop in the other, upping it, then seeing a drop on the other side. The end result would still look like he has 'normal' levels in his water, but that's because massive amounts are instantly precipitating out on pumps, etc. If this is the case, he needs to start dialing back on the amounts he's adding in the same way he upped his dosing volumes.

In either case, there's no other answer, he's adding too much. That's the only explanation for the precipitation. The 'normal' levels he's seeing aren't 'normal' at all, they're what's left over after the precipitation of the excess he's added to the system.

I believe he is using baking soda which he bakes in the oven first. I agree this is the likely the main issue, adding 10x the recommended dosage of this is going to cause a lot of precipitation which builds up on his equipment. The addition of Kalk is likely a factor as well which eats up all the CO2 in the tank, great for keeping algae growth down but not so good for dissolving all the additives.

[Delphinus]

Given that he is dosing Mg then I would agree with your last assessment. But also:

I believe the full 400ml is added at all at once which could be an issue.

I think that is probably it right there, or at least that should be confirmed is the case how it's being added. At the best of times that's quite a sawtooth wave happening, that quick rise in levels is going to have an effect.

[PoonTang]

The Unbaked version (#2) of Randys recipe is the normal one to dose when using Kalk, although i dont know if this would cause any issues. The thing that seems so wierd to me is that he has to add it in such an un-balanced proportion. The 2 part recipies are meant to be dosed in equal portions but he is dosing double the alk as should be needed. Makes me think that something is way outa wack.

[PoonTang]

Originally Posted by Delphinus

Given that he is dosing Mg then I would agree with your last assessment. But also:



I think that is probably it right there, or at least that should be confirmed is the case how it's being added. At the best of times that's quite a sawtooth wave happening, that quick rise in levels is going to have an effect.

I would disagree based on personal experience. I have dumped far more than that in my sump with only a short time between the Cal and Alk being added and never have any precip problems. However if his levels are actually way higher than is indicated than it could be a problem.

[Coleus]

You should try to test his water with your test kits and see the reading. My tank is about the same size as his, I also use Mag 1800 and I have not cleaned it for months. I did not clean my return pump for 2 year with my old one until the front plate got broken :-)

I dose around 80ml for both calc and alk with Randy recipe. But only have small- medium sps corals right now.

[asylumdown]

The only time I got precipitation was when I was doing twice the alk as the calcium, and then I was only adding 150ml of alk to 75 calcium and my pumps were fried in a matter of weeks.

This is first year chemistry:

It's an equilibrium reaction. Calcium carbonate isn't totally insoluble, it's just highly insoluble under normal conditions (like a Ksp of 4.0X10-9 or something). At any given moment in all of our tanks, a small amount of very soluble calcium and carbonate ions are reacting with each other and precipitating out. If things are in balance, the amount that precipitates out equals the amount of calcium carbonate that dissolves back in to the water, favouring the aqueous states of carbonate and calcium. It looks like this:
<-----------------------------------
1Ca(2+) + 1CO3(2-) <----> 1CaCO3

This is highly simplified standard temperature & pressure equation, and when things are normal, you need to worry about pH, carbonic acid/bicarbonate levels, magnesium levels, reaction of carbonate with other ions, uptake by corals, etc. to determine the exact nature of that relationship and how much calcium carbonate you'll produce. But in a balanced system, those other elements that affect that reaction will never lead to pump failures. We're talking about affecting the appearance of molar quantities of calcium carbonate so small you will never, ever notice it in a balanced system (and can barely even measure outside of a lab).

He's adding so much of each, and in such disproportionate ratios, that none of those other, more subtle elements are going to matter. When you provide a gross excess of either of those ions in a solution, you shift the arrow of that equilibrium reaction so that it looks like this:

------------------------------------->
1ca(2+) + 1CO3(2-) <----> 1CaCO3

all the other factors, pH, the relationship between carbonate and carbonic acid/bicarbonate, magnesium levels etc. - none of that matters if you dump so much of one of the primary ions in the above reaction in to the water that you shift the equilibrium way to the calcium carbonate side. Those things are still going on and are important in balanced systems, but the net result of what he's doing is exactly what he's seeing, ruined pumps on a weekly basis.

He's spending money on additives to plate his tank in calcium carbonate.

If I were him, I would stop dosing all additives until things have balanced themselves out. His levels will crash, which will be stressful on the system, but once they're down he can start bringing them back up in a balanced way again.