Diagnosing Sudden Alkalinity - Is this normal?

[IronChefItaly]

Hello everyone, I've stumbled into yet another reefing obstacle and I think I know whats happening but I'd like to get some second opinions in case I'm heading for a crash.

My Current Parameters...(value in brackets is my target)
Salinity - 1.025 (1.025)
Temp - 77.0 (77)
pH - 8.05 (8.2)
Nitrate - 1.50 ppm (1.0)
Phosphate - 0.04 ppm (0.03)
Alkalinity - 7.4 dkh (8.5)
Calcium - 415 ppm (430)
Magnesium - 1240 ppm (1300)

Relevant livestock... (65 gallons display + sump)
6" crocea, 4" derasa and a 2" maxima clam
8" birdsnest colony
10 square inches of plating montipora
an abundance of LPS

The problem... I test my parameters every weekend after i perform a water change and last weekend I recorded the largest drop in alkalinity since I've had this tank (10 months). My alkalinity went from 8.4 dkh to 7.6 where historically my values are solid if I'm not intentionally messing with them. To correct the difference, I raised my daily dosing of reef fusion (pre-mixed two part) from 7ml a day to 8ml a day. Typically I only adjust an additional ml every few months to compensate for ongoing coral growth. This weekend I test again, and my alkalinity values are continuing to fall to 7.3 dkh.

The question... I'd like to interpret this sudden demand increase as a result of booming coral growth but I am slightly concerned that something else more detrimental may be the cause. Is it reasonable to expect to see such drops in alkalinity? I have decided to start testing every three days and I also adjusted my dose from 8 ml to 9ml in hope that my alkalinity will begin to rise. Lastly, what dkh would I start to see rapid tissue loss or in other words, the "danger zone" to avoid?

Any thoughts, advice or experience would be highly appreciated and please feel free to ask for any other details. As always, thanks for reading!

[intarsiabox]

If you are getting lots of coralline algae in your tank, it's a big alk user

[newbie2]

The drop doesn't seem all that bad if it's really only 0.3 in a week. One thing to not is that it says you are testing after a water change. It's always good to test before and after to ensure you don't get a low Alk batch of salt. Do you test the Alk of the salt after mixing prior to the water change? The Monti caps really suck up the chems once they start accelerating their growth as well

[dino]

You have 3 clams? Those will use a lot of alk and calcium.i normally test the tank and knew salt prior to water change

[IronChefItaly]

intarsiabox... bit, but its been there for a while

newbie2... 0.3dkh decrease after I had already increased the daily dose by ~14% in the week prior following the 0.8dkh decrease.

dino... true, but I would expect their calcium and alkalinity demand to be more consistent. As for my salt, I use H2Ocean and I always toss it around between buckets to ensure I've mixed whatever settlement may have happened during shipping. My mixed saltwater consistently tests around 10 dkh. Interesting points though, might be worthwhile to run a batch of tests before my waterchange, a few hours after, then the next day.

Another thought, I use 500ml dosing containers so I run nearly 3 months before having to top them off again. At the moment they're quite low so maybe the alkalinity mix separated out in the container or lost some potency?

Otherwise I'm trying to think of some change in my tank that could account for the sudden draw.

[adam84]

How many times per day is your alk dosing? (One time at 8ml per day or 2 times at 4 ml per day) also are you testing it around the same time every day?

[whatcaneyedo]

The tank is not even one year old and you've stocked it with many coral and inverts that will progressively utilize more calcium carbonate as they grow. I'd say that this increase is absolutely normal. When my former 120gal display was full of large colonies it would drop over 1 DKH per day if the calcium reactor was not running. Soon you may want to graduate to an automated DIY 2 part dosing system or calcium reactor yourself. Buying premixed additives and constantly measuring them out sounds expensive and tedious.

[tang daddy]

Something to note, when I had higher po4 my tank used less ca and alk and as soon as my po4 dropped from .24 to .06 the corals started growing faster and alk had to be readjusted... why not use some buffer to get the alk slowly back to where you want it and then leave the 2 part to maintain it.
You can mix some sodium bicarbonate to your ato so it adds little amounts everyday to bring it back to 8.5.

If you have lower phosphate, alk at 7.5 is totally fine. I keep mine at 8.5 right now as I like corals to grow faster.

[IronChefItaly]

adam84... "How many times per day is your alk dosing? (One time at 8ml per day or 2 times at 4 ml per day) also are you testing it around the same time every day?"
I have a three channel kamoer dosing pump and the 8ml is split into three times throughout the night.

whatcaneyedo... "The tank is not even one year old and you've stocked it with many coral and inverts that will progressively utilize more calcium carbonate as they grow. I'd say that this increase is absolutely normal. When my former 120gal display was full of large colonies it would drop over 1 DKH per day if the calcium reactor was not running. Soon you may want to graduate to an automated DIY 2 part dosing system or calcium reactor yourself. Buying premixed additives and constantly measuring them out sounds expensive and tedious."
Reef fusion is a premixed two part and I am dosing it through an automated pump so it's pretty easy and reasonably priced. You do have an interesting point that brings me some comfort. At 6 ml I was compensating for 0.3 dkh of alkalinity consumption daily and at 8 ml now is only 0.4 dkh. From that perspective it seems reasonable to dismiss the sudden consumption to a spike of coral growth.

tang daddy..."Something to note, when I had higher po4 my tank used less ca and alk and as soon as my po4 dropped from .24 to .06 the corals started growing faster and alk had to be readjusted... why not use some buffer to get the alk slowly back to where you want it and then leave the 2 part to maintain it.
You can mix some sodium bicarbonate to your ato so it adds little amounts everyday to bring it back to 8.5.
If you have lower phosphate, alk at 7.5 is totally fine. I keep mine at 8.5 right now as I like corals to grow faster."
My calcium level is more or less in the right ratio to alkalinity so I'm reluctant to adjust it with sodium bicarbonate – what would be the benefit of doing it that way? I performed all my maintenance and tests yesterday and following your guys' advice I tested the alkalinity before and after. My results were 7.8 dkh before changing out 20% and 7.95 dkh a few hours afterwards which is line with what I would expect. I am continually surprised as to how difficult it is to maintain stable parameters. Each time I think I have it down, something happens and I have to correct - it's been a long process of micro improvements.

At my current rate, my alkalinity should be restored to 8.5 dkh around Friday. Do you guys think this is too quick of an adjustment? should I lengthen the adjustment another week or do anything differently? I've also noticed my pH has been falling recently, dropping to around 7.8 at night and peaking at 8.05 during the day where typically those values are around 8.15 and 7.95. Does anyone else experience patterns with their pH and the weather? or is this entirely a consequence of my lower alkalinity?

[FishyFishy!]

You should be able to raise and lower your alk about 1dkh per day. Anything more than this and you could see issues. I dont really see much wrong with what is going on. Your dkh is actually quite good. Mine is terrible, if im not dosing I can easily see 1-2 dkh swings in a day.

PH is actually very relative to alk dosing. Depends on what you are dosing, it will definitely have an effect on your PH in the positive or the negative.