Ca keeps dropping, Mg high, Alk stable

[Velodog2]

I've reviewed all the Holmes-Farley articles and still don't feel I understand this.

I dose BRS two-part equally at 20 ml per day manually on my 18 gal sps tank and do 5 gal water changes weekly with good old Instant Ocean salt mix and 0 ppm TDS RO/DI water.

My alkalinity stays fairly stable at about 9.5, but my Ca slowly drops. I've raised it using excess CaCl solution as high as 430, but when I revert back to equal dosing over a period of weeks it slowly drops back down to 360. Mg meanwhile always tests high at >1500 although I haven't dosed it. I am using good RedSea test kits. I test for phosphorous using a low-level Hanna checker and get around 3-10 ppm, but don't think it's results are very credible. I don't monitor pH or test for nitrates.

In the tank I have good growth on some of my acros, birdsnest, stylos, and some of my montis. However most acros grow very slowly if at all, and some montis sometimes even recede. Color is generally fair, but not great. I have a low nuisance level of hair algae but cannot grow coraline algae.

Does someone with a better grasp of reef chemistry have an idea of what's going on? This isn't easy to me.

 

[ReefMadScientist]

Make sure your salinity is correct. I had the same issues but my refractometer was off somehow.

 

[Velodog2]

I believe the sg is stable at 1.023. I verify it with a refractometer on occasion. I can't say it is impossible that I am not reading it correctly however. How did this result in the symptoms I am experiencing?

 

[ReefMadScientist]

I believe the sg is stable at 1.023. I verify it with a refractometer on occasion. I can't say it is impossible that I am not reading it correctly however. How did this result in the symptoms I am experiencing?

Well in my situation last week my parameters were thrown off for zero reason. My MG was decent at the time with Alk declining. My CA was also messed up and weird.

After I chased the problem for a good week, matters were getting worse. MG went down to 1000, Ca hit 290 and Kh hit 7. Out of answers, the LFS and I were going over the water parameters and he decided to just check the salinity. Yep I was at 1.018 when my refractometer read 1.025. Overall, my water changes were slowly killing my tank due to me mixing at what my refractometer said.

Got my levels back to normal but dealing with a colony with STN at the moment.

 

[Velodog2]

I will try to get some water to a LFS to verify some of the tests and salinity.

 

[ReefMadScientist]

I will try to get some water to a LFS to verify some of the tests and salinity.

Nice hope your solution finding is a quick one

 

[Velodog2]

Thank you. I also need to do some testing on my fresh-mixed water I am doing water changes with. Perusing another recent thread someone made probably an excellent point that for calcium to drop it has to go somewhere, and for me the only places available are calcification by organisms, precipitation, or removal by water change. Although calcification should be accompanied by a drop in alk as well. I'm not sure about precipitation. Back to RHF.

 

[Clapp'sCorals]

Hope this doesn't sound like a simplistic take on this, but I would suggest just not putting so much stress on equal dosing of your 2-part. If your tank is drinking Ca that quick it needs it to be replaced and if dosing extra CaCl got you were you wanted just keep doing that. I've personally never had a tank that consumed both part 1 and 2 equally (and yes, it's my Ca I always dose higher). If you have a sand bed just make sure there aren't any hard spots of sand where your Ca could be accumulating. Hope this helps or at least gives a new thought on your situation

 

[JOKER]

I adjust mine weekly after testing if needed. I dose 6 times a day for a few minutes. I add a minute or subtract to one or the other if needed. Very seldom ever exactly the same for both and I dose 2 part brs.

 

[Velodog2]

I adjust mine weekly after testing if needed. I dose 6 times a day for a few minutes. I add a minute or subtract to one or the other if needed. Very seldom ever exactly the same for both and I dose 2 part brs.

Does it average out over time to be equal amounts of each?

I've certainly considered just doing what needs to be done to keep calcium up and not worry about it, but I would like an explanation of what's going on, given that the theory says alk and ca should be used equally. I usually add ca, then wait ten minutes and add alk. It is a manual process so I dose only once daily.

I checked my sump last night for precipitate and there was none to be found. I run bare bottom in the tank, so that leaves no where for the lost calcium to hide. There is also no calcification evident on the heater. When I add alk there is some local precipitation in the water, but it goes right back into solution if I add in a high flow area. I may try to separate the addition of alk from ca by more time.

I was a little on the pessimistic side regarding my corals in the original post. Most of them are in fact growing even if it's not as fast as I'd like, and growth and coloration have in fact improved in recent weeks with a change in lighting that they have been adapting to.

But, again, growing corals should use alk/ca in equal proportions. That leaves water changes. Mixed some fresh salt water last night and will test it tonight. Another possibility is that my BRS additives are not right, although I mixed them per instructions and this seems unlikely.

 

[JOKER]

I really am not sure if it equals out but looking at my powder it is close. As for time I alternate they are separated by 2 hours but each dose every four hours. I dose both in different points in the sump also in flow. I mix mine by the half gallon, I was manually dosing but didn't like the ph spike the alk gave so I put mine on dosing pumps so it is smaller amounts spread out over day, money well spent saved a bunch of time. I would try maybe dosing twice a day and separate it more and wouldn't worry unless you started using a lot more of one. I don't use the mag either like they recommend but I use tech m.

 

[Velodog2]

Thanks for the reply. Yeah, I am using a lot more calcium. Just trying to work out why and if I should worry, or not.

 

[JOKER]

I wonder if you raised salinity aa touch if it would help. I run mine between 1.024 and 1.025 using reef crystals right now but thinking of changing or cutting with another salt.

 

[Velodog2]

I guess I'm not following the link between salinity and the alk/ca thing.

 

[mcarroll]

Raising salinity raises ALL your numbers in proportion.

If you are mixing your own reagents, make su you are following the Recipe closely. Being off in measuring can throw off apparent balance of your doses.

Corals use Ca and alk (and Mg) for skeleton-building in proportion...no exceptions. However they are not the only consumers in your tank. Many biological processes use alkalinity. Calcium can precipitate with phosphate or other elements. Likewise for Mg...

Assuming you are mixing right, the effects aside from non-coral-usage should be extremely minimal and big variances should be short-lived.

You should be able to get away with dosing Ca, alk and Mg in equal volumes and only need minor corrections - usually to alk - occasionally too keep everything "in tune". In my system (large stony population) I only do this aabout once a month on average, and the adjustment is usually less than 1/3 the volume of a normal dose.....so it's a small adjustment.

I would check all your mixing proceedures, do tests before and after dosing to make sure the doses are having precisely the effect you intend them to (verifies your mixing), test your fresh-mixed seawater, and keep a reasonably aggressive water change regime (20% weekly would be my choice.) until things settle down to "normal".

Hope this helps!

-Matt

 

[reeffirstaid]

I second the mad scientist on checking your salinity. I took a water salinity reading the other day, using my Milwaukee digital refractometer, and it read 1.024, even though the day before it was 1.026 and I hadn't added any top off. How could the salinity drop two points, when a bit of water had evaporated, which would have raised the salinity? Luckily I have a standard refractometer for just this type of scenario, calibrated that and got a salinity reading of 1.025. Needless to say, my refractometer had been off, for who knows how long. Luckily I caught it, before it caused any real trouble, though it's good to have another unit to test your readings against, in the event one starts throwing off fuzzy numbers.

 

[Velodog2]

Thanks for the inputs! I've been raising my calcium back up (again) by dosing 30 ml of Ca solution and 20 of Alk. Alk is steady at about 9.5. Ca is back to 400 as of Sunday night with a target of 420-430.

Matt - I am using the BRS reagents and mixing them myself. I can't say that I was extremely precise in doing this as I simply went off the 1 gallon line molded into the jugs I'm using, but it doesn't seem like that would be sufficient to throw me off enough. I think. If the calcium was precipitating out for any reason - pH, phosphorous, etc - it seems it would leave a noticeable precipitate somewhere. I've looked and have none. I've tested my make-up saltwater for water changes and it has 390 ppm Ca. So that is low. If my Ca is at my target level and I do a water change I am going to lower it. I typically do about a 20% water change weekly. So that is a smoking gun. More reef-centric salt mix would probably help there. The only avenue left for Ca export from solution is biological growth. Corals are growing but you reiterate they use Ca and Alk proportionately. One bogey is a 4" clam I have. Any possibility is would not follow that rule? Regardless it is growing very slowly, although I suppose the shell could be thickening more than I realize.

All - Salinity is a bugbear. I use a swing-arm gauge for mixing, and compare it sometimes to a refractomer calibrated with 0 TDS RO/DI. They always match well. I should use seawater reference fluid for calibration I know, but I do not. However if as is said salinity changes affects all readings proportionately then this is not my problem because I am concerned with changes of one component relative to another.

I need to do some calculations to see what effect the low Ca in my water change replacement water could have. That seems to be the best possible answer. Otherwise I am doing as others have suggested and not worrying about it overmuch.