tank's using alk but little calcium

[greddy1]

Hey guys,

for some time now I have spent trying to get my tank to start using alk and calcium. It finally is using up alk and drops into the 7's about every 2 days at which point about 50ml of alk addition is added. My calcium levels are still the same after continuous water changes around 440 with no need to dose there. Any suggestions on what might prevent calcium draw? My corals dont grow very fast so I assume they arent' using a lot. I dose vodka along with a reactor to keep phosphorus down and I have a MRC1 skimmer in a 20 gallon sump for filtration. I also use aquatinics HO t5 for lighting. Any help is always appreciated.

I should note that this alk addition of 50 ml has been constant so the usage has not increased which might explain why my corals dont grow very fast

[tmz]

That's not uncommon. For every 20ppm of calcium used in the precipitation of calcium carbonate,1 meq/l (2.8 dkh) of bicarbonate/carboante alkalinity is used. You salt mix via your water changes may be deeping up with the calcium side of it but not the alk. Coraline will also use quite a bit.

[bertoni]

I agree. Those numbers seem normal to me. I wouldn't worry.

[greddy1]

I haven't seen as much coraline growth around my rock as I thought compared to some other friends tanks but I guess my main concern was that the coral growth doesn't seem to be constant and is very slow. As long as the numbers seem okay I'll continue to improve other aspects to the tank

[bertoni]

You could try dosing alkalinity daily, which might help a bit. I suspect that there's some other issue limiting coral growth, though.