Problem with kalkwasser and water evaporation??

[rampro6698]

I have a large 600 gal display tank and a total volume of about 750-800 gallons for the whole system. My system is running pretty stable right now with the following water parameters:

S.G. 1.024
dKH 8-8.3
Ca 420-430
Mg 1280-1300
pH 8.23 day and 8.15 at night
PO4 0.006 t0 0.021 (measured by Hanna ULR phosphorus checker)
Nitrates and nitrites undetectable (measured by Elos liquid test kits)
temp 76-78 F

My evaporation rate is about 7 to 7.5 gallons per day. So I am running a Ca reactor with effluent pH at about 6.7 at a steady fast drip and I have a Kalkwasser reactor (Precision Marine) that gets fed by an RO tank and uses a Liter Meter III dosing pump to put 28 Liters of mixed Kalk water into the sump per day. This is all fine except my tank is fairly empty (fairly small bioload of coral and fish) still and my dKH is getting a little hard to maintain at 8 or above. I can maintain Ca, Mg, and even pH fine but my alkalinity will likely need to be added as a supplement of some kind in the future. But my issue is that my kalk reactor is essentially putting in all my evaporation right now as RO water. If I increase the kalk reactor any more (to increase alkalinity) then I will eventually see a drop in SG due to more RO water going into the sump than is evaporating.

I realize all is good and stable right now. But my concern is when I start adding a lot more corals to the tank how will I keep my alkalinity up? I can't use an alkalinity solution because those are made with RO water which is just adding more non-salt water to the sump. I had thought about just running the kalk reactor from the sump itself which would work except I suspect the salt water would precipitate Ca out in the kalk reactor once it is added to that high pH environment. Do you see my concern? Does anyone else have this problem and any thoughts on solutions?

[C.Eymann]

How big is the calcium reactor / what model? Calcium reactors, if sized properly to the system/ demand will have no trouble maintaining ALK at a set rate once tuned to meet demand. Maybe retune the reactor? lower pH in the reactor by .1 or increase effluent rate and bubble count accordingly till you see no fluctuations of ALK in a 24hr hour period, then double check 48hrs later for any change.

[dave.m]

my tank is fairly empty
If you have no real demand yet why are you running either the kalk or Ca reactors? Why not start with an automated top-off (ATO) system first and then add the other reactors back in when you actually have a need for them?

Dave.M

[C.Eymann]

If you have no real demand yet why are you running either the kalk or Ca reactors? Why not start with an automated top-off (ATO) system first and then add the other reactors back in when you actually have a need for them?

Dave.M
he stated he had a few corals, but you also have to take in consideration other calcifying organisms, coralline, tube worms, etc etc. If he is seeing a decrease then it is being used up.

[rampro6698]

Appreciate the feedback. Sorry I didn't respond earlier. I guess somehow my email setting is turned off so I didn't know I had received responses. The tank has been running for about 2.5-3 years and has stabilized to these levels pretty well. The Ca reactor is a large precision marine about 8-9" diameter and about 36" height. I do only have it filled about 1/2 way with ARM Ca media so I may need to fill it all the way. I will try decreasing the effluent pH to 6.5 and see how that does. I was just trying to keep my water pH around 8.2 to 8.3 so I was not sure if increasing the effluent rate and/or decreasing the effluent pH would decrease my water pH too much. I can combat that some with the kalk but again the kalk volume going in is already at the evaporation rate of the system. I am not sure how to quantify the bioload in the system as far as corals. I can say that there is probably only about 15-20% of the coral mass compared to the tank of the month tanks. I mean there is a lot of live rock real estate left to place coral. There is about 750 pounds of live rock in the tank and it is all very "matured" and tank does have a lot of coralline algae.

The coral does seem to be using the alkalinity and Ca and the coral is growing. I don't mean to say the tank is empty, it is just not anywhere close to its capacity as you see with some people's tanks that are packed with coral and they are having to frag out coral just to make room for everything, etc. I am just trying to plan ahead and figure out how my alkalinity will be met when the tank gets to that point. I bet it would work itself out if I filled the Ca reactor up all the way with media. I just filled it half way because I thought the tank didn't need it full at this time but maybe I was wrong. Thanks for the input. Any other thoughts are welcome.

[Vinny Kreyling]

http://reef.diesyst.com/crarticle/crarticle.htm
Give this a read, made things clear for me.