FINDING OUT HOW MUCH PER DAY TO DOSE.

[JCSReefing]

Need help figuring out how much 2 part to dose. I have a 65gallon display with a 15g sump so lets say total system volume of roughly 70 gallons or so. I tested my water alk and came back 8.1 dkh. I want to run my system at around 9-10 dkh which is what I think most people recommend as a good start. Using the BRS alk calculator, states I need to add 95ml to get me up to 10 dkh using soda ash.

What is my next step in figuring out how much a day to dose alkalinity which I believe would be the same for calcium to level out. Then also, how to find out how much magnesium to dose once I figure out my alkalinity/calcium per a day?

 

[dbl]

Start by testing parameters on day one and recording results. Then let tank run for 3 or 4 days without any dosing. Test again and record results. The difference divided by the number of days will give you your daily usage. You then can use the various calculators to determine how much of each element you need to dose daily.

 

[Randy Holmes-Farley]

Trial and error dosing is how to zero in on a final dose. The above method is fine to get a rough dose, or you can just pick a smallish stating dose and try it and adjust as needed.

 

[McMullen]

Just remember to add small amts. Your coral may not appreciate going from 8 to 10 all at once.

 

[JCSReefing]

Perfect. I just did a 10g water change so I will give that a day or so. Then check alk, calcium, magnesium and record it. Then wait 4 days and do it again and check back here for confirmation I'm doing it right and have the right amounts.
Is it correct that whatever I dose for alkalinity, you want to dose the same amount per day or week as calcium?

 

[McMullen]

My Alk and Calcium consumption are not equal. I use more Alk, so probably shouldn't make that assumption.

 

[Randy Holmes-Farley]

My Alk and Calcium consumption are not equal. I use more Alk, so probably shouldn't make that assumption.

How much more? What exactly are you dosing?

The primary reason for that difference is water changes.

 

[Randy Holmes-Farley]

Perfect. I just did a 10g water change so I will give that a day or so. Then check alk, calcium, magnesium and record it. Then wait 4 days and do it again and check back here for confirmation I'm doing it right and have the right amounts.
Is it correct that whatever I dose for alkalinity, you want to dose the same amount per day or week as calcium?

That's what I would do unless calcium needs a one time correction if very low, or is already too high. Calcium doesn't change enough relative to testing accuracy to gauge its demand in a few days.

 

[McMullen]

@Randy Holmes-Farley, nope....not from water changes. Been a while since I've added up total ml from doser. Last was almost 2:1

 

[Randy Holmes-Farley]

@Randy Holmes-Farley, nope....not from water changes. Been a while since I've added up total ml from doser. Last was almost 2:1

Must be an off mix or dosing pumps not delivering what is claimed (common). The actual demand cannot vary that much from the ratio of about 18-20 ppm for each 1 meq/L (2.8 dKH) of alkalinity unless the actual demand for both is very low (in which case tiny contributions such as from dosing nitrate and producing alkalinity that way add up to a significant amount).

I discuss reasons for actual and perceived demand differences here:

When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-12/rhf/index.htm

 

[Randy Holmes-Farley]

If you use a sulfur denitrator, that uses alkalinity and may skew the apparent demand ratio in some tanks.

 

[bgoldb]

If you use a sulfur denitrator, that uses alkalinity and may skew the apparent demand ratio in some tanks.

That may explain my constant alk to calcium imbalance with my alkalinity running perpetually low even after dosing washing soda while calcium testing at 500. I have been using one half of a Brightwell xport No3 brick for about 3 months which comes infused with sulfur. My total water volume is only 20 gallons so I have a good feeling this is the culprit. On the bright side, I have no nitrates.

 

[McMullen]

2 part and dosing pumps. No sulfur reactor.

Pump accuracy......not sure....and a moot point. The point is don't assume a 1:1 ratio.

Useage of Alk and Ca in my tank fluctuates and as my tank has matured into large SPS colonies my Alk consumption surpasses Ca. This is not a fluke in just my tank.

 

[JCSReefing]

so if i take my initial 8.1 dkh and after say 2 days its 7.3 dkh, thats a diffrence of 0.08, divided by 2 days is 0.04. how does that show me how much to dose?

 

[JBradford]

This is the same problem I'm having. I'm been researching the big 3 heavily. And I know what I'm using per day. And I want to offset that usage but raise the overall levels. There is all kinds of info about what to do but not a lot I can find about the numbers and how to determine how to do it.

 

[McMullen]

Check out the BRS calculator. That got me close. Then, next step was to check levels every day and start tweaking. It took a good two weeks to dial in my doser pumps. Keep in mind this is a rinse and repeat process as coral grow. At least for Alk, make checking a regular routine.

Adding up daily consumption then converting to ml's did not work for me.

 

[JBradford]

Right now I'm manually dosing, as today is day 3. Debating the pumps, my idea is manually dose while I get the numbers where I want them and then get pumps to maintain.

 

[West1]

following...

 

[Rick Gaas]

Following...

 

[Scott.h]

As mentioned, I'd be really careful going from 8 to 10. What, and how many corals do you have? I have an 85 total water volume softie tank that uses 8 ml per day of the BRS ash. But it depends on what's in there. Why do you want to raise it to 10?