How much calcium does a good sized Derasa consume?

[rhitee93]

My tank is about a year old. I have quite a few coral and a small maxima clam that have all been showing good growth for a few months now, but water changes have been enough to keep my calcium in the 450ppm range. I've been expecting to have to start dosing one of these days, but have been waiting until the numbers say it's time.

A week and a half ago I out a fairly large Derasa in the tank. It's 7-8" long, and this week my calcium has dropped to 406ppm.

I use the Hanna tester, which I know many people don't like, but I have always gotten consistent readings with it. Now I'm wondering if a clam can have that much impact in a week, or if this mostly/partly a testing error. Unfortunately that was my last packet of reagent so I can't retest today.

System is a 120 with 108 gallons of water. I do a 10 gallon water change each week and use IO Reef salt. Here is a FTS from today:

Here is what my calcium has done since March. There is certainly a downward trend which you would expect given the coral growth. What I don't know if I should just start dosing with the new clam in place, or wait a another week or two to see what happens.

 

[dansyr]

50ppm Ca drop in 100 gallons over a week feels like a lot. The alk trend decreasing the last week, yes 100%, the magnitude of the drop, i would be surprised if it wasn't actually 30ppm or something.

A gut check I do sometimes as a way to intuit if it's precipitation or increased uptake is calculate how many grams of CaCl2 that would take to precipitate for that change. Just to figure out if it's abiotic precipitation or actually related to coral/clams growing, or is an unreasonable amount. In my 20 gallon clam tank, 10ppm change Ca equates to about 2 grams of Ca precipitated (for example). in ~110 gallons, I think your 50ppm change means about 50g Ca - i.e. do you think your system added 50g skeleton in a week. Biomass, sure; skeleton, unlikely.

 

[rhitee93]

Thanks! I appreciate the calcs on ppm to mass of skeletal growth. That's a useful sanity check.

Yes, my alk consumption has gone up over the last few weeks. I haven't taken the time to learn how that is related to calcium yet, but that will probably be tonight's reefing lesson. I like science, but there is so much to learn in this first year that I haven't gotten around to working through the big 3 chemistry lessons yet.

 

[minus9]

It's time to start dosing, as water changes will only take you so far. Pick a method for 2 part additions and keep doing water changes and you'll be just fine.

 

[rhitee93]

Yeah, it seems like it is time.

After spending the weekend reading articles and watching a few videos I've decided to go the limewater/kalkwasser approach. I just need to decide how I want to dose it.

 

[minus9]

Yeah, it seems like it is time.

After spending the weekend reading articles and watching a few videos I've decided to go the limewater/kalkwasser approach. I just need to decide how I want to dose it.

I'm old school, so I just mix up 5g buckets of kalk and dose the clear effluent. Another option is to dose TM all for reef via their dry powder mix.

 

[rhitee93]

I'm old school, so I just mix up 5g buckets of kalk and dose the clear effluent. Another option is to dose TM all for reef via their dry powder mix.

I'm thinking that my needs are going to be so low that I may do something similar. Just mix up the solution and pour in what I need each day. At least to start. I'll probably add a dosing pump eventually because my tank is at work so I don't see it every day.

 

[minus9]

I'm thinking that my needs are going to be so low that I may do something similar. Just mix up the solution and pour in what I need each day. At least to start. I'll probably add a dosing pump eventually because my tank is at work so I don't see it every day.

You need to dose throughout the day very slowly.

 

[reefnfun]

How much calcium and Alk. will a large Deresa clam use? quick answer, all of it. I have a large Deresa and a Gigas. I use a calcium reactor and b-ionic 2 part 120 ML per day