Well, crow-eating time approaches....

AllSignsPointToFish

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I've always run my reef tanks with an alkalinity around 10 dKH. The rationale was that this value represented the middle ground in the alkalinity range given in care guides for most corals (8-12 dKH). LPS has done well in my tank as long as I have some detectable nitrates and phosphates. SPS other than Montipora seem to struggle or exist but not thrive. I test frequently, dose aminos and carbohydrates, dose trace elements, do water changes and other routine maintenance, but Acropora and birdsnest really seem to struggle in my tank. I have added calcium hydroxide to my topoff water and trim calcium levels in the tank through dosing for the last 3 years or so.

After exhausting all of the other options and through some encouragement from my local reef club members, over the past two weeks I've been running a test to see if lowering the alkalinity to around 8 dKH would really make a change. I stopped all ATO water additions and have been dripping limewater continuously throughout the test period while using my sodium carbonate solution to round out and stabilize dKH numbers. To my surprise, the tank has really looked much better since I lowered the alkalinity. Not only is polyp extension crazy good right now, even the birdsnest is looking markedly better and the long tentacle anemone is, honestly, the largest I've ever seen him. Thus, the case for change is established.

Right now, the dKH is holding steady around 7.7-7.8. I can only conclude that the lower alkalinity has really helped my tank (hence time to eat crow) since I've held other factors as constant as possible. However, dripping limewater continuously is a major PITA. I've overall mostly matched the drip rate to the evaporation rate through manual trial and error so that salinity has been constant, but there's no practical way for me to drip continuously into the foreseeable future on a 125 gallon system.

So, I have some questions that I hopes some of our peeps might be able to help me get a handle on:
1. The evaporation rate is 2-4 quarts per day, depending on time of year and temperature. Dripping that amount of limewater in not feasible in the long-term, and dosing the better part of a gallon of limewater per day is also not going to work out well for the life of the dosing pump. I have an Apex Classic with an EB8 (no unused outlets...so I'd have to address that), and I was thinking of just setting up a topoff routine where I run the pump for a few seconds several times per day. Does anyone have a better suggestion for dosing that amount of solution each day?
2. I've used standard old Instant Ocean forever, with reasonable results. IO also mixes up a dKH higher than 7-8, so how would one adjust the dKH of the freshly made saltwater before adding it to the system? Can one use hydrochloric acid to adjust the dKH? Is it an iterative procedure or is there a calculation that one can do to estimate the amount of acid required to lower the carbonate hardness to a desired level? I'm scared to death at trying a different salt mix because the last time I tried a different salt (Reef Crystals), it was not a pleasant experience.
3. I recently was reading about Randy's newer two part solution using sodium hydroxide and sodium sulfate. I'm curious about switching to this system eventually, but the transition plan for his classic DIY recipe to this new arrangement is not clear to me. I'm particularly concerned about the sulfate portion as it was tied to magnesium in the past but is now divorced from magnesium additions. How would one make the switch if I decided to do that in the future?

Sorry for the long post and questions. I hope someone will be able to give me ideas on how to proceed going forward. Thanks in advance!
 

BeejReef

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Congrats on your improvements!

If you want to stick with a single dosing head, you might consider that tropic marin carbo calcium stuff.. much more concentrated than limewater and probably not as hard on your doser. On the other hand, you have an established system.. just an idea.

I use IORC and IO. Alk rise from 15% weekly wc is pretty tiny.. like .2dkh. Usually comes down on its own. If I think of it, I disable kalk dosing for the evening to offset.

Following cuz I'm curious what u come up with. Have been dosing saturated kalk w dosing pump from a separate reservoir myself and letting pure RODI keep the level. Doser holding up so far. Will see.
 
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AllSignsPointToFish

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Thanks for the feedback! My water changes are monthly and on the order of 25-30%. I don't know if I just had a bad batch of Reef Crystals last time or if my system wasn't doing so well and the small shock from the salt change just precipitated problems.

I like Randy's newer DIY system because it would require two reservoirs instead of three (which would free up one dosing head). I also like that the new recipe does a better job raising pH than the previous version, and it probably does a better job than limewater.

I want to add another 4-head dosing pump to dose Red Sea Coral Colors and Reef Energy, but I really don't need THREE dosing pumps in my cramped space. I already dose vodka, sodium carbonate, calcium chloride, and a magnesium chloride/sulfate mixture. I suppose as long as one is testing during the swap to dial in calcium, magnesium, and carbonate hardness, the actual solutions used don't really matter?
 

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What is the reason you're adding kalk and 2-part (or just the alkalinity part)? As for the alkalinity issue, you can use gallons of water X number of kh drop desired X .123 to figure out how much muriatic acid you need to get to desired levels (this is for 33% HCl, the low fume variant requires more). I typically use 4.5ml of low fume in 5g of water bring IO down to about 7.2dKh.

Edit: and for what it's worth, I dose nothing but 2-part and things look pretty good.

Edit 2: Even with water changes in the 25-30% range, you still shouldnt be getting an alkalinity spike high enough to bug any of your corals. I'd look into other factors being problematic if that remains the case at the lower levels you're running now.
 
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AllSignsPointToFish

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What is the reason you're adding kalk and 2-part (or just the alkalinity part)?
I had issues with pH control when I was dosing only two-part, so I started adding limewater for better pH control and did the fine-tuned alkalinity adjustment with the sodium carbonate solution and the dosing pump.
 

ScottB

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I had issues with pH control when I was dosing only two-part, so I started adding limewater for better pH control and did the fine-tuned alkalinity adjustment with the sodium carbonate solution and the dosing pump.

Just a thought. You might find it easier to control/increase pH with a recirculating CO2 scrubber/skimmer combo. I only touch the thing once a month to swap media and it keeps my range to 8.0 to 8.3.
 
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AllSignsPointToFish

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Just a thought. You might find it easier to control/increase pH with a recirculating CO2 scrubber/skimmer combo. I only touch the thing once a month to swap media and it keeps my range to 8.0 to 8.3.
I tried the CO2 scrubber. It did work but I tore through media at the rate of $20 per month or more. I have my skimmer plumbed to the outside for fresh air, and that helps some.
 

homer1475

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To lower the DKH its a simple calculation:

Water volume x DHK drop x .123 = ML of acid to add

Example, 20 gallons of water with a DKH drop of 2

20 x 2 x .123 = 4.92ML of acid. I would just do 5 myself. Just remember to let it agitate for 24 hours prior to use as the acid significantly reduces the PH.

I've done this for years with IO and a gallon bottle of muriatic acid lasts me nearly a year with weekly 10G WC's.

I find at 1.026 IO mixes up to around 10DKH and I drop it down to 8.
 
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AllSignsPointToFish

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To lower the DKH its a simple calculation:

Water volume x DHK drop x .123 = ML of acid to add

Example, 20 gallons of water with a DKH drop of 2

20 x 2 x .123 = 4.92ML of acid. I would just do 5 myself.

I've done this for years with IO and a gallon bottle of muriatic acid lasts me nearly a year with weekly 10G WC's.
I'll do the carbonate neutralization calculation to validate the 0.123 conversion factor. I think I know where that comes from, but I want to be sure I understand.
 

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