dangerous drop in pH?

[Richard DeChamplain]

Randy,
I need your help. Where should I start. First my tank parameters are outlined in my name board,but in brief 600 gallons reef 200 gallons sump and plumbing, high tech lighting and circulation with moon cycles mild,moderate, and heavy storm circulation, mechanical and bio filtration and a dialyseas machine monitoring salinity pH,ORP and performing 8 gallons a day of water changes.
My system has been up and running for 3 years with a slow 6 month start up from h2o to filled with live rock. over the last 2.5 years everything has gone very well with the exception of 2 major events and one chronic problem/nusience that has almost lead to a catastrophic failure. the first two events: 1 calcium reactor stopped working and while waiting for newer bigger model to be built and a little (lot) of procrastination my calcium level dropped to about 100(probably for several weeks) and I lost two acros but could have lost more. 2 while out of town my conductivity probe stuck resulting in a gradual increase in salinty to 1.032 I was able to bring this back to 1.025 over a two week period without losing any corals but I did loose all of my large feather dusters and several crabs.

Now on to the main question/nusience Ca++ and pH. My tank sucks Ca++ I have well over 200 corals all happily devouring Ca++. I have used CaCl solutions with dose pumps I have used reef complete( calcium gluconate?) with dose pumps these both work well but I have always felt like calcium carbonate and Calciumhydroxide were the best most bioavailable calciums to provide. Therefore I run a Ca++ reactor but the reactor cannot provide enough calcium without dropping my pH. My reactor is 4 foot tall. this low pH is the bane of my existence. My range is 7.95 to 8.2 with normal functioning. The 7.95 in the morning scares me. Therefore, I started useing a nilsen reactor aprox 2 weeks ago in line with my autofill from my dialyseas unit. the autofill function supplys ro/di h2o this passes thru the reactor and into my sump. the sensor for activating the autofill has a pretty wide range and therefore it may not add topoff for a couple of days and then may add 4 -5 gallons over 12-24 hours.

For the first few days after I started using the new reactor Everything looked great pH range 8.05-8.34 ca++ 450+had a noticible burst in growth in some of my faster growing sps then three days ago my calcium reactor blocked I cleared it with the usual silt production apon restarting but my pH started to fluctuate/drop again. The next morning the pH dropped to 7.9 with some retraction of a couple of soft corals. I started my lights a few hours early and by lights off the pH had returned to 8.15. the following morning the same thing happened but I noticed that my 20 inch table acro that recieves a direct current from one of my storm pumps had excess slime and one small area of tissue loss. I made the assumption that the pH was the problem but did not rule out a localized effect of a piece of kalk or other caustic agent lodgeing in the coral and burning it. I was very concerned as you can imagine and tested eveything except alkalinty(I didnt have one at the house) ca350-400 all others excellent. I recalibrated my pH probe and to my horror the probe read 7.74. I immediately cut back on the co2 entering the calcium reactor and slowed the rate and began adding kent supperbuffer via a dose pump over the next 24 hours. The pH this morning was 7.98. I'm pretty sure the damage to the table acro has stopped and the sentinal soft corals looked good today as do all of the other sps.

Do you have any suggestions.
Did my kalkwasser exhaust my buffering capacity?
I still dont have an alkalinity test value for you but do you think the calc consumed the calcium carbonate.
Do you have any suggestions on how to maintain a more stable pH.

I'm open to any and all suggestions/advise?

thank you in advance. I apologize for the rambling but quite frankly I'm very frustrated.
DrDe

[Richard DeChamplain]

dKH was 9 last night. pH this am 7.95...?

[Richard DeChamplain]

Also I have since read your sugested articles in this forum, but without the dKH at the time of the problem I'm unclear on the culprit. I'm changing out my probe today to verify my readings.

[Randy Holmes-Farley]

Did my kalkwasser exhaust my buffering capacity?


No, that wouldn't be it.

But low alkalinity leads to low buffering and potentially lower pH.

A pH of 7.95 is rather typical of aquaria using CaCO3/CO2 reactors. The best ways to raise it are to use some limewater, and more aeration with fresh air.

In a tank like yours, you might also consider a balanced two part additive like B-ionic or my DIY (using baked baking soda) on a dosing pump.

[Richard DeChamplain]

Thank you for your response. My current plan is continue with kalcreactor for autofill but drip into a pvc baffle in my sump to provide a little more mixing time before it enters the main tank especially on heavy storm days. And I'm considering adding it only at night. continue using calcium/co2 reactor. For now I plan to continue useing reef complete by seachem for additional Ca/Str/moly. Do you have any thoughts regarding this arrangement? Specifically Reefcomplete.

I will look into B-ionic

[Randy Holmes-Farley]

My current plan is continue with kalcreactor for autofill but drip into a pvc baffle in my sump to provide a little more mixing time before it enters the main tank especially on heavy storm days.

What is a heavy storm day?

[Richard DeChamplain]

Heavy storm= two additional Iwaki100rlt alternating flow direction on a loop from the sump to the display tank ie total flow provided by four Iwaki 100 rlt instead of normal day where flow is two 100 rlt. when these days come up in my cycle the passage time through my sump is fast, therefore I was concerned the high pH limewater may not have time to equilibrate before being expelled onto my corals...very localized high pH.

[Randy Holmes-Farley]

Oh, I get it. I was thinking of an actual weather phenomenon that was somehow impacting evaporation or something.

How fast would the limewater be added from the reactor?

[Richard DeChamplain]

It enters via a dose pump. The pump ran in three cups in 5 minutes last evening. The pump is activated by a float switch with a relatively wide range so it may not run for two or three days and then run a lot the next.

[Randy Holmes-Farley]

As you probably know, that isn't the optimal way to dose limewater.

Do you replace all evaporated water that way?

[Richard DeChamplain]

yes, all evaporative loss is replaced this way. But I probably should put the limewater reactor on its own dose pump?.

[Randy Holmes-Farley]

How much evaporation do you have?

If you added all of 2-3 days worth of evaporation (or even 1 day) in a few minutes, that would be a big problem as the pH will go very high..

If it were on a dosing pump, and still connected to the float switch, that would be a good setup (that's what I use), as it will be delivered slowly, but only when needed.

[Richard DeChamplain]

The pump does not add that fast, again 3 cups/24oz in 5 minutes in a 200 gallon sump->600 gallon tank seems ok to me but the total volume over 12-24 hours may be as high as 8 gallons. The pump is a standard peristaltic dosepump.
At this point after reading your articles I'm less freaked out about the pH and I am most likely going to place the reactor(limewater) on its own pump.

[Randy Holmes-Farley]

Ok, if you add a half gallon or less at a time to a 200 gallon sump, that would be fine. :) I was worried about more like 5 gallons from several days of evaporation.

[Richard DeChamplain]

Thank you so much for your patience.

[Randy Holmes-Farley]

You're welcome. :)

Good luck!