help with low Ca and slow-dosing experiment

[johns]

Randy-

Stilll struggling with trying to keep Ca levels where they should be in my 75G SPS heavy tank (plus a few clams). I use kalk for all my top off which is generally a gallon a day, and I dose the home-made 2 part recipe at ~120 mls/day and levels fall...fall...fall... I have no Ca reactor. And when I checked my Ca this morning it was Ca 330 and Alk 10.5dKH. These have been out of balance for a while now, and I have a question about correcting that (see below)

I want to experiment a bit with using a dosing pump to dose the home-made recipe. In the past i had been dosing the 120ml in 2 chunks. 60mls of each in the morning, and 60 at night. My thought is that maybe adding so much of each all at once will cause more to precipitate and not go into the water column. So I bought a peristaltic pump capable of delivering the solutions much more slowly. So now I have it set to deliver just about 5 mls each hour so that my 120mls is delivery slowly throughout the day.

Any thoughts on whether that might help?

And on to my imbalance. Prior to the water change I did yesterday, my Ca was 280 and Alk was the same, at 10.5. So you can see why I am a bit concerned about getting my Ca up (I do water changes monthly, but the way things have been falling, the water changes are starting to not cut it for bring the Ca where it should be). According to the reef calculator, an Alk of 10.5 should have a balanced Ca of around 435, which is probably right where I would like to be coincidently. Is it ok for me to just dose Ca to get close to the that level without adding anything additional for the Alk. I have Kents Liquid Ca (or the home made part 1) that I could use to do this.

Or is there something else you would use?

I'd like to get to where I want to be first, then start this experiment with the slow dosing with the pump to see if I can get thing working how I want.

 

[Randy Holmes-Farley]

My guess is that you are just not adding enough of the calcium part for some reason. If precipitation were the problem, alkalinity would be low.

I'd boost the calcium to 420 ppm or so over 2 days, and then continue with the two part dosing. You might need to regularly add more of the calcium part than the alk part if for some reason the mixtures are not as expected. Maybe try 1.5x as much of the calcium part daily (compared to the alk part) and see what that does over the course of a week (not a day).

 

[johns]

Kind of makes sense. I think I started seeing more rapidly declining Ca once I started using the dosing pump. This was also right at the same time that I made a new batch of home-made stuff. But previous to this, my Ca and Alk have both always been on the low side. Only recently did my Alk shoot up high relative to the Ca. So maybe my idea of the slow dosing will still work once I get the dosing of the 2 in line relative to each other.

Any thoughts on using Kents Ca liquid vs the home-made Ca solution to bring it back up? Probably the same thing, but I think I know more about the actual ppm of the Kents Liquid (esp if my Ca solution may be off somewhat, like you say), so it might be a bit easier to predicatbly change my Ca levels using that.

After I get it to around 420 Ca and 10.5 Alk, I think I'll continue the same way I have been for about a week for so and see if Ca still falls more relative to Alk to try to verify if this is my problem.

So, if they were being used properly for coral growth they would both fall relative to each other, right?

And you're saying if something precipitates they will still fall the same one relative to the other?

 

[Randy Holmes-Farley]

Any thoughts on using Kents Ca liquid vs the home-made Ca solution to bring it back up?

There will be no significant difference. If your home made one is low in calcium, it will just take more than expected.

FWIW, you may also have an inaccurate calcium kit (or user error).
So, if they were being used properly for coral growth they would both fall relative to each other, right?

Yes, whether corals use it or it precipitates. Alkalinity falls by 1 meq/L (2.8 dKH) for each 18-20 ppm drop in calcium.