Low alkalinity levels . . . and falling.

[justinx]

I have been dealing with this for a little bit now and have exhausted all my ideas to no avail. Possibly there is something that I have missed.
Heres the deal . . . I ran out of my test kits a while back, and went about a month and a half without testing. I know, shame on me, but I kept intending to order them online because the LFS charges triple what swf.com sells them for (salifert). Anyway, I finally got around to ordering them and when I tested everything, my levels were only slightly off. Not too bad. Here are the numbers.
date pH Alk Ca
3/16 8.2 3.43 430 These were pretty much standard for 6mo
3/24 8.2 3.54 ? Ran out of Ca kit
4/10 8.2 3.66 ? Ran out of Alk Kit
5/19 8.4 3.25 485 New salifert kits
5/25 8.4 3.43 470
6/5 8.4 3.31 465
6/10 8.4 3.09 460
6/18 8.4 2.86 450
First off, do these numbers seem strange to anyone? They do to me, but all corals/animals look happy and continue to grow as far as i can tell.
The additives that I use are both powdered form of seachems reef builder and reef advantage calcium. I have been using these from the start and have been pleased with the results, but now am wondering if this is the root of my dilema. The alk buffer claims that it will cause pH to stabilize at 8.3 with longterm use, and since my pH test is only accurate to even intervals I am thinking that the pH is at 8.3 instead of 8.4. I use FasTest which only reads to 8.0, 8.2, 8.4, and 8.6. I drip top off RO water with the additives dissolved in them at a slow rate to avoid precipitation so I dont think that it is.
Any ideas out there?
Thanks

 

[broomer5]

JustinX
If you've not experienced cloudy water, or seen any white precipitation in your tank ..... you've not exceeded the saturation point of calcium carbonate.
I doubt you have from your numbers.
Your first set of test numbers on March 16th are textbook perfect in my opinion.
On 3/24 and 4/10 - there's no telling what was going on. We can make some assumptions .. but that's all.
Did you continue dosing the tank as you normally did for the 6 weeks or so you were without kits ?
You got the new Salifert kits for alk / calcium.
If you continued using the FasTest for pH, and your pH has really increased - then you may want to back off on the dosage amounts of Reef Advantage and Reef Builder for awhile.
Normally - saltwater will not hold as much calcium at higher pH values. Normally.
We're assuming your pH is at 8.4 now.
Do you do your tests at the same time of the day ?
What time do you do these tests ?
What is your specific gravity or salinity reading ?
What temperature do you keep ?
Your numbers don't look bad really.
We shoot for ranges - not exacty values.
Our test kits just aren't that good to begin with - and maintaining a decent range is much easier than trying to be too exact.
If this was my tank - I would back off on the calcium/alkalinty products somewhat - but not stop entirely.
Keep testing now and then and keeping track as you have.
I would not raise the alkalinity at this point either - until the calcium comes down some too.
If you're pH was down around 8.0 so lower - you could bump the alk up some. I wouldn't at pH 8.4 though.
Again if it was my tankwater - I'd back off on additives, wait for the calcium to drop back to the 400-420 range - then work to raise you alkalinty if needed.
Getting it back to your 3/16 values would be ideal in my opinion.

 

[bang guy]

Normally I agree with Broomer's superior understanding of Ca/ALK but in this case I believe you're adding tohe appropriate amount of CA. I'm basing this on the falling CA levels and the is falling at nearly the appropriate rate when compared to the CA consumption rate.
I think you just need a one-time bump up of ALK. The tool I would use in this situation iis Baking Soda (Sodium Bicarbonate).
I don't see a tank size so I would suggest an extra tsp per day of Baking soda for each 50 gallons of water in your system until ALK is in line with whatever the CA level is that day.
Eventually you're going to have to bump up your additives to maintain CA and ALK levels.

 

[justinx]

Well, since my sig is gone, i can list some more details. The tank is only a 20H that is lightly stocked with LPS, and Softies, and 3 sps (hydnophora, pocillopora, and a pachyseris) The LPS are a Frogspawn and an open brain. The temp is at 82, and the salinity is around 1.024-.025 (refractometer).
The way that I add as of now is 1/4 tsp of each product dissolved in RO water on alternating days. I always add at night after the lights go out, and my tests are always done in the evening after the lights have been on for a while.
I am going out of town for the weekend, so there is not much that I can do as of now, but once I return, i think that I may try a "double" dose of alk buffer and see what happens.
Also, I have never seen any precipitation in my tank during or after adding. I drip them in pretty slowly, so I don think that is a problem.
Another thing that I have just thought of is when I do my weekly waterchanges, the batch of new SW that I am currently using has not been buffered at all because it was mixed when I was tihout test kits. Do you think that by doing 5% weekly water changes with "raw" SW (instant ocean) could also be contributing to the problem? I am mixing some new stuff right now, so we will see what happens with that before I do anything brash yet.
Thanks for the help guys.