Chronic Low Alkalinity- 5.7!

ThePurple12 · Jul 27, 2020

Hello! For the last 2 months (at least, that's as long as I've been testing), my alkalinity has been extremely low- around 5.7. I added baking powder one time to around 8dKH, but it came down again quickly.

My corals aren't doing the greatest, unlike my dinoflagellates...

What should I do? What could be causing this?

loui · Jul 27, 2020

if your alk is getting lower once you achieve your goal you need to continue to add ALK to keep up with consumption. Only way to find out what your daily consumption is, is by testing every day once you get things locked in you can go every few days for testing. Some people test more some test less depends on your tank and the corals you have. I am going to assume that your calcium and mag is also low. Doing water changes will help getting your parameters in check, but you will need to continue to test and re-supply the necessary elements to maintain a balanced environment.

Silent · Jul 27, 2020

Sounds like you might need to start daily dosing.

ThePurple12 · Jul 27, 2020

The weird thing is, I only have one medium acro colony and several SPS frags/small colonies in a 125g. Is there anything besides consumption that lowers alkalinity?

loui · Jul 27, 2020

coralline algae

Larry L · Jul 27, 2020

What are your Calcium and Magnesium levels? If your Magnesium is low, it makes it easier for the Calcium and alkalinity to combine and precipitate out of the water.

jimc40 · Jul 27, 2020

Get a affordable dosing pump. If you are consuming alk calcium is probably also being used

ThePurple12 · Jul 27, 2020

Last time I checked, calcium was 400ppm. I don't have a magnesium test kit.

loui said:
coralline algae

I forgot about coralline, good point

chipmunkofdoom2 · Jul 27, 2020

ThePurple12 said:
Hello! For the last 2 months (at least, that's as long as I've been testing), my alkalinity has been extremely low- around 5.7. I added baking powder one time to around 8dKH, but it came down again quickly.

My corals aren't doing the greatest, unlike my dinoflagellates...

What should I do? What could be causing this?

I hope you mean that you dosed baking soda. Baking powder can contain significant phosphate and aluminum.

How quickly did the alkalinity drop after adding? What is your calcium and magnesium? What is your salinity and how do you measure it?

ThePurple12 · Jul 27, 2020

chipmunkofdoom2 said:
I hope you mean that you dosed baking soda. Baking powder can contain significant phosphate and aluminum.

How quickly did the alkalinity drop after adding? What is your calcium and magnesium? What is your salinity and how do you measure it?

Yeah, I meant baking soda.

I’m not sure how quickly because I tested about a week after adding the soda. I just added some more today to 7.5 dKH and will test every two days.

Salinity is 35ppt measured with refractometer. Magnesium is unknown (no kit) and calcium is 400.

chipmunkofdoom2 · Jul 27, 2020

ThePurple12 said:
Yeah, I meant baking soda.

I’m not sure how quickly because I tested about a week after adding the soda. I just added some more today to 7.5 dKH and will test every two days.

Salinity is 35ppt measured with refractometer. Magnesium is unknown (no kit) and calcium is 400.

Alkalinity dropping over a week is not unusual at all. Most people have to supplement alkalinity every day to keep it stable. I would not expect to maintain alkalinity by dosing once a week.

It's a bit unusual that your alkalinity is 5.7 dKh. Alkalinity doesn't tend to get this low under normal circumstances since most calcification gets progressively slower the lower alkalinity drops. Where do you get your saltwater? If something is wrong with the saltwater, you might be dropping alkalinity with water changes.

Low magnesium could also be causing precipitation.

ThePurple12 · Jul 27, 2020

It's RODI with Reef Crystals salt. What causes low magnesium?

chipmunkofdoom2 · Jul 27, 2020

ThePurple12 said:
It's RODI with Reef Crystals salt. What causes low magnesium?

Not very many things. Magnesium tends to drop very slowly compared with calcium and alkalinity. If there's something wrong with your salt mix, the saltwater you're making could be deficient in magnesium. It's hard to say since you don't test for it.

Bad salt mix could also explain the low alkalinity. I don't think "bad salt mix" happens as often as reefers claim it does, but bad batches of salt do undoubtedly make it out. Try testing new saltwater after you mix it. Let it mix for several hours before testing. If the alkalinity is not 10dKh or higher, there's probably something wrong with your salt mix.

ThePurple12 · Jul 27, 2020

I'll try testing some water, thanks

jccaclimber · Jul 28, 2020

I used to have a tank that would pull down to around 5 if I didn’t stay on top of it. Everything looked ok to me, but it sure did look a lot better when I started dosing on a daily basis!
I consider 0.5 dKh per day to be perfectly normal. I currently have a tank that I’m still filling out (although there is a 6” clam) and it consumes 1.7 dKh per day, at least according to the BRS calculator.

AT 50% SPS coverage in a past system I would see the sort of drop you are experiencing in 24 hours if I stopped dosing, so it isn’t unreasonable.

If you’re low, add more. Just make sure it’s going in slowly to a high flow area so it doesn’t just precipitate out.

ThePurple12 · Jul 28, 2020

chipmunkofdoom2 said:
Not very many things. Magnesium tends to drop very slowly compared with calcium and alkalinity. If there's something wrong with your salt mix, the saltwater you're making could be deficient in magnesium. It's hard to say since you don't test for it.

Bad salt mix could also explain the low alkalinity. I don't think "bad salt mix" happens as often as reefers claim it does, but bad batches of salt do undoubtedly make it out. Try testing new saltwater after you mix it. Let it mix for several hours before testing. If the alkalinity is not 10dKh or higher, there's probably something wrong with your salt mix.

Well, I mixed a bucket and waited a while and it tested at 9 dKH.

I guess I just didn't know alkalinity could get so low in a reef tank by coral growth. ;Facepalm

ThePurple12 · Aug 16, 2020

I didn't dose for a week and my alk is now at 5.1... I feel like something's wrong here.

jccaclimber · Aug 16, 2020

You stopped dosing and so you ran short. What is unusual about that? Your tank is consuming it. If you stop replacing the consumed alkalinity then the levels will go down.

ThePurple12 · Aug 16, 2020

Right, but it just seems weird that it would get so low. Has this happened to anyone else?

blasterman · Aug 16, 2020

Alkalinity is not like calcium. Alk is consumed by all kinds of biologic processes in your tank and can deplete rapidly. Younger tanks can eat as much as a full point of dKH per day. This is normal.

With no SPS load alk consumption will eventually stabilize.