Alkalinity Woes

[madducks42]

We're having some trouble maintaining alkalinity in our tank. My boyfriend posted on another forum but didn't get a lot of responses so I stole his post and thought I'd try here since you guys have been pretty helpful so far : )

First, for context our setup is:
RedSea Reefer 425XL (88gal display & 24 gal sump, ~100gal of actual water)
Its been up and running for about 5 months.
It currently contains:
2 ocellaris clown fish
1 royal gramma
1 peppermint shrimp
2 skunk cleaner shrimp
1 bloodfire shrimp
1 purple tang
1 potters angel
1 condy anemone
1 rainbow bubble-tip anemone
1 brittle star
misc snails and crabs (CUC)
2 small clumps of waving hand xenia
1 hammer coral frag
2 tiny polyp frags (1 polyp each)
1 medium polyp frag
1 small torch coral
1 lavender hairy mushroom
1 small maze brain coral
~70 lbs of Pukani rock

DIY ATO system that adds 1-2 cups of water at a time, as needed
Most of the coral is relatively new to the tank, with the polyps and the hammer coral being the "oldest", and added about 10 weeks ago.
Around that time we started a very slow drip of kalkwasser mixed as potently as possible (2 teaspoons/gal). This would add about 1/2 gallon of fully saturated kalkwasser over about 5-6 days. Before starting the kalkwasser I adjusted the magnesium, calcium, and alkalinity using the BRS bulk kalkwasser starter package (kalkwasser, calcium chloride, sodium bicarbonate, magnesium mix).
The calcium levels decreased very slowly (~5ppm/day), but alkalinity dropped ~1.0 dKH per day. I've been adjusting the alkalinity manually with the sodium bicarbonate solution every day or two. As we added more coral I decided to switch to adding the kalkwasser directly to the ATO. I started with 1 teaspoon/gallon. Again, the calcium levels dropped very slowly (~2ppm/day), but the alkalinity continued to drop around 1.0 dKH per day. Even after upping the potency of the ATO kalkwasser to 2 teaspoons/gal, the alkalinity still drops ~0.75 dKH/day
pH is varies between 8.0 and 8.20 pretty closely following the lighting schedule. That's up about 0.1 since I switch to kalkwasser in the ATO.

So, what are we doing wrong? I was under the impression that kalkwasser would be "the" answer for a tank with a low/medium load, providing stable calcium and alkalinity. The tank has a few different types of coral, but they're all pretty small, so I can't imagine the load is very high. And the calcium levels are dropping, but just a bit. But the alkalinity falls off pretty quickly. We do weekly 10-15% water changes.

Suggestions?

 

[mcgyvr]

Its not uncommon for tanks to use unequal amounts of cal/alk..
I use 2 part because of that.. My alk usage is far more than my cal usage..

In a "perfect world" they are used in a specific/equal ratio.. Our tanks aren't the perfect world..

I'd suggest going to a 2 part (individual alk and cal solutions) and a multi-head dosing /peristaltic pump or continue manual dosing

I skimmed your post and sorry if I missed an important detail..

 

[JohnZena]

I had the same problem. I started using Reef Fusion by Seachem and within 3 days my system balanced. Madducks42 is 100% correct. A 2 part should solve your problem. Reef Fusion parts 1 and 2 by Seachem is what was readily available for me.

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[thegrun]

Your calcium/alkalinity consumption ratio is not that far out of line, 10ppm of calcium consumption should be close to 1.4 dKh of alkalinity, so your 5ppm of calcium versus 1.0 dKh of alkalinity isn't that far out of ratio, and certainly within the margin of error of our hobby test kits. What is more concerning to me is what is consuming the calcium and alkalinity in the first place. What are your magnesium, calcium and alkalinity levels? Unless you have a lot of coraline algae growth, I suspect the problem may actually be that you are massively overdosing and your tank is supersaturated and calcium precipitation is driving your calcium/alkalinity consumption. Are you seeing any signs of calcium precipitation like a white build up on your glass, sand clumping or pump impellers? Are you using a "reef" salt mix that is already high in calcium and alkalinity? If there are any signs of calcium precipitation I would switch to a standard salt mix like Instant Ocean, stop using kalkwasser and dosing anything. Wait a couple of weeks until the over-saturation dissipates and then test and balance your water chemistry.

 

[madducks42]

@nero0762 can speak more to the specifics of what we're doing for dosing. These are the levels from the most recent test:

Alkalinity: 9.3
Calcium: 450
Magnesium: 1400

There hasn't been any calcium buildup so far. I'd have to check what our salt mix has when I get home, but we've been using the same salt mix since before we started dosing. What counts as " a lot of coraline algae growth"? We started to see coraline algae a little over a month ago. At first it was just a few spots, about 3 weeks ago it was probably 10-15 spots scattered around the tank. Now I'd say there are at least 100 different spots of it. It's not like the live rock is coated in it or anything, but if you look at the rock you start to notice spots of it everywhere. It's definitely growing fast but not sure if that's fast enough to be what is consuming the calcium and alkalinity.

 

[dublo8]

be careful with the kalk. Keep the amount used steady and follow the 2 part dosing as necessary. check every day until your good.

I also second the use of a dosing pump. it takes a bit to balance things out and understand your specific tanks dosing regimen but you'll get there. Things are growing so you have to expect the depletion and it's line with your Ca usage.

 

[thegrun]

It seems very likely to me that you have over saturated your tank and need to stop dosing calcium and alkalinity and stop using kalkwasser until there is a demonstrated need. It seems very unlikely that your tank needs much if any dosing at this point given the small amount of stony corals you have in the tank. Your water chemistry looks fine, although I would let the alkalinity fall to around 8.0 dKh. I would recommend switching to a salt mix low in calcium and alkalinity, make a 15% water change, test your parameters and wait a week to see where things shift to. You may see an initial drop in alkalinity and even calcium, but don't panic, wait to see if things stabilize after a week without dosing or using kalkwasser.

 

[madducks42]

My concern with stopping dosing and letting everything drop is that the alkalinity will probably plummet to around 7. We don't have a lot in the tank but we are steadily adding new frags/corals every 4-6 weeks. And the hammer coral looks noticeably worse when the alkalinity drops below 9.


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[ReefyGra]

My concern with stopping dosing and letting everything drop is that the alkalinity will probably plummet to around 7. We don't have a lot in the tank but we are steadily adding new frags/corals every 4-6 weeks. And the hammer coral looks noticeably worse when the alkalinity drops below 9.


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Bear in mind that hobby test kits are not exactly perfect.

I have a Salifert Profi Kit and a Red Sea Pro Kit for Alk, and they differ by 0.5dkh consistently. I just aim for 7dkh for my ULNS tank, so 6.8 vs 7.3

The Ca kits are even worse with one telling me 420ppm and the other 480ppm, and their response is not even linear.

The trick is consistency, not aiming for a particular target.

Regards
Graham.

 

[madducks42]

We've been testing every morning for the past two weeks, usually using the Hanna checker and the Red Sea kit, definitely noticed a difference between the two. Our goal is to keep it stable around 9.5 and we've mostly been able to do that the last week. This has been accomplished by keeping the kalkwasser going and adjusting the alkalinity with a sodium bicarbonate solution every day. We were doing this before but every 2nd or 3rd day, now we're doing that in smaller doses every day which seems to keep all the levels stable. We're debating if we just want to get a two part dosing system and if we do which one. We do have an Apex but I think the two part dosing system that works with that is $300.