what is your alk level and how do you lower it?


New member
here is a list of my water chemistry that I took recently

pH - 7.8-7.9 (been at this all summer)
Nitrates - 0-5
Nitrites - 0
Ammonia - 0
Calcium - 410
Mag - 1395
Alk - 11.5

I would like to bring my alk down to about 8-9 and maintain it around that level too. I have read that water changes bring it down by according to this link, the brand that I use has an alk level of 11 already with is IO so water changes will keep it at 11.


How do you guys bring your Alk down?


New member
You can just wait and it will drop on its own as long as you have things calcifying (corals, coraline, clams, whatever). I just did the reverse of this with calcium. I dosed alk but not ca for a few weeks to bring it down a little.


New member
I can do that but the problem is that my Salinity is now getting to 1.024 and I keep it at around 1.026. I have been topping off with fresh water and now that its down to 1.024, I am going to need to top off with some saltwater to get it to .026 again and that will probably keep it up there for awhile.


New member
Its in the OP. I am using IO regular salt and according to that link I posted, the alk is at 11 for it. I haven't tested it myself though when I make a fresh batch.


New member
How big of a tank? Why the salinity swing? Is it going to your skimmer? I would just bring your salinity up and then wait for it to drop before adding any more alk. You can continue the calc part though. I assume you have coral since you care about these numbers, so it should only take a few days to bring it down. When you do water changes, just don't dose for a day before hand and then for a day or two afterwards.

Is there a reason you want bring the Alk down? Are you dosing alk? How often do you do water changes (and how large)? You might be able to get away with just doing weekly water changes to keep your alk up depending on the tank size and coral demand.

Edit to add: you should also test your newly mixed saltwater to see what numbers you are getting. The numbers are often different than the "average" supplied elsewhere.


Premium Member
The dKH at 11 should be safe enough for a short period. I'd get the SG back up, and just stop dosing any alkalinity supplement. Most tanks consume alkalinity at a rate high enough that water changes shouldn't be that much of a problem. If your tank still has a high dKH, about all you can do is dose a mineral acid, like muriatic acid, into the fresh water for changes, to lower the dKH.


Still Learning
If you don't have a very high demand for alk and calcium in your setup then use another brand of salt that has a lower alk. I don't know one off the top of my head since I also use IO.


Active member
Increasing your Calcium level will reduce your ALK a little. I like to mix IO salt with Oceanic, as Oceanic is low in ALK and much higher in CA. The two together great a nice balance.


New member
I checked my alk last night and it seems to have dropped down to 10.3. Not sure how it got up to 11.5 before but I will need to check the levels of newly made water.

Didn't check my calcium last night but I will recheck cal, alk, and mag tonight. What are the ideal levels for best coral growth or is it different for every tank?


Team RC
As long as they are kept within the following ranges all should be well. You may tweak within the ranges if you feel it is necessary.

Alk: 7-11dKh
Calcium: 375-475
Magnesium: 1200-1400