Lowering KH on Older Tank

[jackers]

I have searched here but it seems that people who need to lower their KH have established tanks with lots of corals.

My tank has been up and running for a few years now. It has been a FOWLER tank for most of it. It is an 85 gallon tank with a 10 gallon sump. I use RO/DI water for top offs and water changes. I have about 80-90 lbs of live rock.

I am in the process of adding corals to it now. Currently, I have two clowns, a hawkfish, and a tang. I also added two frags, one torch and one duncan. I do 10% water changes weekly with a 20% change about once a month.

I bought the Bulk Reef Supply 2-part kit with dosing pumps. My test kits are Elos CA and MG, Salifert KH.

Tonight, I tested my tank before a 10% water change. Here are my numbers:
Mg - 1150
Ca - 190
KH - 10.5

I am planning on using the calculator on BRS to get my Ca and Mg up but it doesn't say how to get my KH down.

Any advice?

 

[Dr. Reef]

why do u wanna lower the alk? unless ur running an ULNS (utra low nutrients system) meaning nitrates and phos absolutely 0 then u need to keep ur alk at 7-8 range other wise a wide accepted range would be 7-12dkh. while ur cal is extremely low at 190, it should be 380-440 range and should not be increased more than 50 ppm per day. and mag is also low at 1150 it should be increased at no more than 100ppm to 1280-1400 range.

 

[jackers]

why do u wanna lower the alk? unless ur running an ULNS (utra low nutrients system) meaning nitrates and phos absolutely 0 then u need to keep ur alk at 7-8 range other wise a wide accepted range would be 7-12dkh. while ur cal is extremely low at 190, it should be 380-440 range and should not be increased more than 50 ppm per day. and mag is also low at 1150 it should be increased at no more than 100ppm to 1280-1400 range.

Well, the reason I was wondering is, I've read that KH was directly tied to Ca levels. Meaning, if my KH is high, my Ca would be low. I was wondering that if I raised my Ca, would my KH raise as well? Seeing as how it's already at the high end, I was worried it would shoot higher.

 

[Nano sapiens]

Calcium and alkalinty occur in saltwater in a specific ratio, but they are not 'joined at the hip' as you suggest where they must go up or down together.

You need to raise your calcium level, so you need to use a product that does that specifically (not a balanced '2-part' product which would raise both). For example, Seachem's 'Reef Complete', which also supplies some Mag and Strontium. Alk will typically drop over time, unless your WC salt mix has high Alk.

Once your Cal and Alk are at the desired levels, then you would switch to a balanced 2-part product to maintain both (if needed).

 

[tmz]

First verify the alk test results.

If accurate

Just increase the calcium to abut 400 ppm (50ppm per day) and let it run for a while .Remeasure.

Alkalinity can be reduced with muriatic acid( 1/11,000th of water volume = - 2.8dkh) ;95 gallons is 3785.4ml x95= 359613 divided by 11,000= 32.7ml of muriatic acid will reduce the alk by 2.8 dkh. I'd do less than half of that per day but
I don't think it is worth it . 10.25 is ok even with low nutrients and will come down when there is enough calcium to support calcification, even if it's only by coraline algae.

 

[bertoni]

That alkalinity level is fine, and there's no useful direct tie between the calcium level and the alkalinity level. I wouldn't dose muriatic acid into the tank. If you stop dosing any pH buffers or other alkalinity sources, the level should drop on its own if there's any coralline algae growth.

 

[csauer52]

Can you just let the Alk come down on it's own over time and does Ca to bring it up where you want it? That's the approach I would take, slow and steady changes to get things where you need them. Nothing is this world responds well to large/abrupt changes and our tanks are no different.

Just my opinion.

 

[bertoni]

Alkalinity will drop on its own over time, although potentially very slowly. Only water changes or dosing an alkalinity supplement (which include pH buffers and some tap water) will raise the alkalinity.

 

[tmz]

It drops on it's own unless you add it. Bringing the calcium up encourages carbonate alklainity to be used as calcium carbonate is formed.

 

[jackers]

Thanks guys! I set my dosing pumps up to intermittently dose to bring my Ca and Mg levels up within four days. Thanks for the help.

 

[bertoni]

You're welcome! Good luck!