SPS depleting ALK?

[Hiker4twenty]

I've got quite a bit of SPS in my system now and they're all doing really well and growing. In my alk testing I've noticed that my levels are dropping very slightly with the same dosing I've been doing for months now, which has kept it at 9dkh. Will the addition of more SPS use up more alk in my system and cause the need for me to adjust my dosing?

Maybe this should be in the water chemistry section. Mods please move if you feel I have posted in the wrong thread category.

 

[Melosu58]

I`m interested what your calcium is. Usually alot of SPS corals will suck up all the calcium in the tank.

 

[Hiker4twenty]

I tested the calcium as well and it was at 450. It could be anywhere between 400 and 450 because my test only reads in 50ppm increments.

 

[ccCapt]

Dave, when corals grow their hard skeletons (calcification), that process uses aprox 1 meq/l (2.8 dKH) alk to 18 ppm calcium to 2 ppm mag. If there is an increase in alk consumption, there would also be an increase in ca and mag consumption.

 

[Hiker4twenty]

Thanks Larry. It might just be my test kit then. It's about 5 months old.

 

[sen5241b]

I dose alk every day but I do not have to dose Cal but maybe once a month. I don't doubt the depletion formula above but chemistry is complex and there are always exceptions.

Do you have lots of coralline? It will suck alk (carbonates) out of the water.

 

[Melosu58]

Dave, when corals grow their hard skeletons (calcification), that process uses aprox 1 meq/l (2.8 dKH) alk to 18 ppm calcium to 2 ppm mag. If there is an increase in alk consumption, there would also be an increase in ca and mag consumption.

That`s why Larry is my Guru. Good info Larry.

 

[Hiker4twenty]

I do have a lot of coralline so that is definitely a contributing factor. I tested my alk this morning and it was at 8dkh, but it was only about 10 min after I dosed the tank. Would testing that soon after dosing possibly give an inaccurate reading or will the alk dosing have an instant effect?

 

[ccCapt]

The dosing will show instant results in a test as long as the chemical that was supplemented gets thoroughly mixed in with the tank water. After 10 mins it would show in the test result.

 

[Hiker4twenty]

Thanks Larry. I'll test again when I get home to see where it's at. I still need to pick up a new kit just to be sure.