High Alk, how to bring down?

[-JB]

How do you lower Alk? Mine has been slowly rising and tonight I measured it at 16.8 dKH

What do I do to bring it down? I use RO/DI water for topoff. it measures 3.2 dKH. I also drip effluent from a Ca reactor the effluent measures 31.4 dKH.

[ July 08, 2001: Message edited by: -JB ]

 

[-JB]

^ anyone?

 

[DEADFISH1]

doing a few good water changes is the only thing I can think of, usually your fighting too keep it up, adding calcium will bring it down also, do you have an idea of what's causing it to go up?

 

[jdeets]

Is the elevated alk making your Ca level crash?

I'm really surprised that your RO/DI has alk of 3.4 dKH. My RO/DI has alk of zero--it changes color with one drop of reagent.

Your problem is that your topoff water is adding an alkalinity component to your system and is not simultaneously adding any Ca componenet. What is happening is that you're adding biomineral components in an unbalanced fashion to the tank.

What I mean is that a freshly-mixed batch of synthetic seawater should have Ca and alk components in a relative balance. Additionally, your Ca rxr is adding alk and Ca in a balanced manner. What does this mean? If your RO/DI water had no alk component, then you'd be adding Ca and alk to the system in the same ratios that they would be consumed by your livestock.

Since your RO/DI has such high alk, when you do water changes or top off, all that extra alkalinity in the RO/DI is "extra." You see, without the extra alk, you would already be adding Ca and alk in the proper proportions for consumption of your livestock. So the extra alkalinity is building up in the system. (Or, more accurately, the carbonates and bicarbonates are building up.)

How to fix this? You need to increase calcium input using an unbalanced method. First, turn the CO2 to the Ca rxr off. That will prevent the Ca rxr from adding any more alkalinity to the system. That will also prevent it from adding Ca as well. So you'll need to supplement with Ca (either CaCl2 or some IONIC liquid Ca supplement--do not use a Ca supplement that is bound (like with sugar) as that will be incompatible with your current supplementation methods).

With the CO2 turned off, the alk will have a chance to come down. Ca will also fall along with it, so you'll need to support Ca with one of the supplements I mentioned. Once alk and Ca are in line again, start the CO2 flowing again.

With such high alk in your RO/DI water, you're going to continually fight this battle, because every time you top off or do a water change, you'll be adding "extra" alkalinity. To offset that, you'll have to constantly be adding supplemental ionic Ca, either with CaCl2 or an ionic liquid Ca supplement. You might consider looking for another source of topoff water. Or perhaps your DI filter is exhausted and a change of your RO/DI filters would help.

For the long-term, if you cannot come up with a "clean" water source, you might consider not using the Ca rxr, especially if topoff water and water changes are enough to keep your alk within limits. Then you could just supplement with Ca to complement the alk that's ambient in your RO/DI water. Since your RO/DI water is not permitting you to maintain a balanced system, using other balanced supplements (like a Ca rxr or kalkwasser) won't work well for you--you'll continually have rising alk and never really have it balanced.

If you'll continue to use the Ca rxr, adjust it based on your system alkalinity--to maintain it around 10-11 dKH. Then use an ionic Ca supplement to keep the Ca elevated.

Unless you can find a source of fresh water without any alkalinity component, you'll be fighting this battle forever and you'll never enjoy the benefits of balanced supplementation that a Ca rxr would normally provide.

 

[-JB]

My Alk doesn't seem to drop much after a water change, last water change my Alk dropped from 15.7 to 14.3 dKH. In all honesty my Alk has been between 14-15 dKH since I set up the tank about three months ago. All other parameters seem to be fine, I have been battling to get my Ca above 400 with a Ca reactor for the past 1 1/2 months. In the last week I have finally got my Ca levels to stay at a constant level. I have been dosing Kent Turbo Calc to help get Ca levels up, but I thought that would lower alk if you didn't use buffers, which I don't. I really don't know what is causing the Alk to stay so high. Maybe my effluent's Alk is too high at 31.4 but I've read it's best to keep it about 3x what you want your Alk to be.

 

[-JB]

I am going to re-test my RO/DI water tonight. I think I made a mistake in the test and it probably is lower than what I posted. I did the test last night in haste and just dumped a few drops in instead of one a time. Noticed that it turn pink almost right away and just adjusted it to 3.2.

 

[jdeets]

Yes, JB--if your RO/DI really has alk of 3.4 dKH, then you won't see your alk come down much with a water change. Test your freshly-mixed seawater, and you'll see that it will be unbalanced, with higher alk and lower Ca. That's from the additional alk in the RO/DI.

To get your Ca higher, you're first going to have to lower alk. What is your current Ca level? It most likely won't go higher until the alk comes down.

Since the Ca rxr adds Ca and alk in balance, you can crank the effluent out all day and not see your Ca go appreciably higher. (For each change in dKH of 2.8, you'll see a change in Ca of 20 ppm, when using balanced supplementation. That means that to raise your Ca, using the Ca rxr, by 40 ppm, you'd have to increase your alk by 5.6 dKH from its current level. Not desirable in your situation.) As you can see, you've got to establish a balance in the system before the rxr can really do it's job, because a Ca rxr cannot be used to change one biomineral component without changing the other in this ratio. (The actual ratio is 20ppm Ca vs. 1 meq/L alkalinity.)

What you need to do is get your system balanced. Turn off the CO2 to the reactor. As your alk falls, add CaCl2 to keep the calcium AT ITS CURRENT LEVEL. Once alk is down to 10-11 dKH, start the rxr again and adjust it to maintain the proper alk level. Then increase the amount of CaCl2 you're using to get the Ca up to where you want it. (Don't try to elevate the Ca until the alk is in line--otherwise, you'll just be fighting against yourself and wasting chemicals...) Once everything is balacned, the reactor should then keep your Ca and alk in check, except that if your RO/DI is really that high in alk, you'll always have to supplement Ca to keep the system balanced.

Be patient--this whole process will probably take anywhere from 2-4 weeks.

 

[jdeets]

I just reread your last two posts--and noted that you have gotten your Ca level stabilized. The reason it has stabilized is that your are already using the CaCl2. And yes, using this product without using a buffer will lower your alk. This is not necessarily a direct result of using the turbo calcium--but happens because you'll only be adding the Ca component and no alkalinity component when you use this product. The result is that you maintain Ca by constant input and the alk comes down due to calcification by your livestock. (i.e., your livestock is consuming both Ca and carbonates/bicarbonates, but you're only adding the Ca so the alkalinity drops.) But this is exactly what you need to do in your case.

 

[-JB]

Ok, I just had my wife measure the Alk of the RO/DI make-up water, The Alk is zero, turned pink on the first drop. My bad.

When I say my Ca has stabilized, I mean I have been able to get the Ca to stay at a contanst level of 385-390 for about a week with no CaCl2 additions, just using the reactor. But I did use the CaCl2 to originally get the levels up from about 320 to their present level of 390. My reactor is going pretty strong to be ale to keep up with the present levels of the tank. My effluent is 76ml per/min and the BPM is about 190!! (checked and I have no leaks anywhere). Even with this high level of CO2 output my effluent is at a pH of 6.78 and Alk of 31.4 dKH.

So If I read you correctly I should shut off my reactor, until my Alk drops into the 8-9 dKH range. Then start it back up. Should I dose CaCl2 during this period? I have 4 LPS 2 SPS in the tank, they are all medium to large size so they use Ca. I am thinking I should just dose the CaCl2, no reactor and wait for my Alk to drop.

 

[jdeets]

That would work. Since your makeup water is OK, you might want to just crank the reactor back to about 20 mL/min and adjust your CO2 so that your effluent pH is about 6.8. See if your alk starts dropping and use the CaCl2 to keep the Ca up. Turning off the reactor would get you in line the fastest, but just cranking back on the effluent flow rate and a corresponding reduction in CO2 in put should also do the trick.

My reactor is set at about 1500 mL/hour and I keep the effluent pH below 6.8 with only 20-30 bubbles/min. I think if you reduce the effluent flow rate and the CO2, let the alk drop that way and add the CaCl2 to keep Ca elevated, you should have it balanced in no time. Going forward, you could probably continue to use the slower effluent flow rate and CO2 injection rate and it should keep itself in pretty good shape.

To "turn off" the reactor, just shut down the CO2--don't turn off the reactor completely because you don't want it to stagnate in the reaction chamber--keep it circulating, and the effluent flowing, in other words, so that you don't build up nasties in the reaction chamber.

Once it's balanced, you'll be amazed at how nicely the reactor will keep everything balanced for you!