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View Full Version : Super ALK drop . . What would cause that?


QuiGonJay
03/07/2015, 02:08 PM
Some background: 9 month old tank, only 2 small sps coral frags(duncan and candy cane) the rest soft. Actually a Caribbean rose too, unsure if that is lps. Decent coralline growth and 2 oyster hitchhikers on live rock. Parms consistent for lat 3 months at around 390/400 calcium, 7.8 ph, 9 to 9.5 alk, 1390 mag, 1.026 salinity and 20/30 nitrates.

Last measurements were 2 weeks ago and marched the above. Kept with my weekly 2 part reef dosing (reef builder) for calcium and alk and every other week water change. Today, measurements are like the above with one exception, alk dropped to about 6.4! I measured twice to be sure. Test kit is red sea. What would have caused such a drastic drop? The only change was I started a skimmer 2 weeks back. Working ok and pulling skimmer but hasn't really moved nitrates much yet. Could a skimmer put alk out of whack? Tank inhabitants seem fine but such a big drop kind of freaked me out. Thanks!

Sk8r
03/07/2015, 02:15 PM
Coral may have started to feed. This would blitz the calcium, and the alk would plummet---but the other part of this triangle is the magnesium level. If your mg is 1300, the alk should stay up as long as corals are ok with the calcium. If this won't hold, you may need more supplement. Never used 2-part, myself...honest question here: will it feed stony corals ok or might you need a kalk drip?

killinit123
03/07/2015, 02:21 PM
if I were to guess its that your mag is low do you test for mag? the reason being that mag provides buffering capacity by bonding with carbonate ions(alk).because mag is binding up carbonate it allows for more carbonate in the water than if mag wasnt there at all. when mag levels are appropriately high it allows for the addition of calcium without the associated drop in alk.

does that make sense to you? i know it can be confusing maybe someone has an easier way of explaining it

QuiGonJay
03/07/2015, 02:27 PM
Mag has been consistently at 1390ish. That is the weird thing. All the inter relationships but calcium, mag and ph really haven't changed in 2 weeks. Just the alk. Have had the small frags for around 4 months and the dosing with 2 part seems to have done fine thus far with parms in the range mentioned in my first post. perhaps this falls in the category of ' sometimes weird stuff happens' which isn't uncommon in this hobby I guess. ; ) so what is the adverse impact of low alk?

lllesley
03/07/2015, 02:31 PM
Mag has been consistently at 1390ish. That is the weird thing. All the inter relationships but calcium, mag and ph really haven't changed in 2 weeks. Just the alk. Have had the small frags for around 4 months and the dosing with 2 part seems to have done fine thus far with parms in the range mentioned in my first post. perhaps this falls in the category of ' sometimes weird stuff happens' which isn't uncommon in this hobby I guess. ; ) so what is the adverse impact of low alk?

I have had a couple of batches of asw for water changes that were low in alk, do you check your water before WC's.
Just a thought.

killinit123
03/07/2015, 02:41 PM
your calcium is a little low at 390-400 it should be at 425.. also your mag is a little high at 1390 it should be at 1300... although these are not way out of range this could have a negative effect on your alk because as your mag is high and binding up the alk calcium is low and fighting with your alk to correct itself making alk drop.. just my opinion by lowering mag tot he appropriate levels this should correct your problem

QuiGonJay
03/07/2015, 02:41 PM
Salinity yes, but not alk.

QuiGonJay
03/07/2015, 02:44 PM
Killinit123, thanks. But how would you lower mag? Other than water changes and the two part reef builder which is calcium and alk, I'm not adding anything. Other than crazy coralline growth how would I decrease the mag?

Sk8r
03/07/2015, 02:45 PM
Possibility too of an expired alk test: a bad test can lead to calcified pipes as you dose to chase a fictitious deficiency. Get a crosscheck and confirmation on that alk result from your lfs.

QuiGonJay
03/07/2015, 02:48 PM
Sk8r. Good point. With everything else pretty normal maybe the test kit suddenly went weird. Gotta say, the testing in this hobby is stressful for me!

killinit123
03/07/2015, 02:51 PM
Killinit123, thanks. But how would you lower mag? Other than water changes and the two part reef builder which is calcium and alk, I'm not adding anything. Other than crazy coralline growth how would I decrease the mag?

that my friend I do not have the answer to i would assume a water change would bring it to the required level depending on what type of salt you use but at the same time you have to take into consideration a water change is only going to affect the amount of water taken out

killinit123
03/07/2015, 02:52 PM
Possibility too of an expired alk test: a bad test can lead to calcified pipes as you dose to chase a fictitious deficiency. Get a crosscheck and confirmation on that alk result from your lfs.

+1 I didn't even think about that its worth a try before you go doing anything crazy