Long term use of Lime

[seased]

Great article on the use of lime! I have been using lime for the past 4-5 months in my 55 gallon reef. I use a float switch in the sump to control the amount of kalk/makeup water that is dosed into the sump. I would guess that about 1-2 cups of kalk is pumped into the system when the switch is activated. This is for makeup water, so it runs 24/7.

Here is my question - after about 2 months use of lime/kalk, when I clean my pumps and powerheads, a hard, calcium type residue forms on the pump shafts and sometimes on the pump magnets. Also, this forms on the heater.

Is this just something that goes along with the use of lime/kalk, periodic cleaning of pumps, or am I dosing the lime incorrectly - maybe too fast? My alk stays around 3.5 Meg/L and my calcium is in the low 400's. Thanks for your help!

[Randy Holmes-Farley]

That precipitation is from excessive calcium, alkalinity, or most likely pH.

Do you know how high the pH gets in the vicinity of those devices that are getting coated?

[seased]

I have a pH meter with the probe located in the tank. The buildup happens on powerheads in the tank as well as the return pump and heater in the sump. Last night, a little before lights out, the pH was 8.42. About a month ago, the pH was reading in the 8.5-8.6 range. I thought the meter might be off, so I recalibrated using the borax method you mentioned.

Also, I measured the Magnesium - using a Salifert test kit, and it read 1300. I use Kent salt and try to do 25% water changes every 2 weeks.

I have tried using kalk/lime several times in the past. One time the buildup on the pump shaft was so bad that it actually stopped the return pump. I just make it a point to completely clean the pumps about every 2 months.

Should I put the probe in the sump where the kalk is pumped and see what the reading is? I really like the idea of using kalk but just want to figure out/understand if this periodic cleaning is normal or if I am doing something wrong. Thanks for your help.

[Randy Holmes-Farley]

Yes, I'd check the pH in the sump. You might consider mixing some viengar into the limewater (45 mL vinegar per gallon of limewater) to help reudce the tank pH. More aeration will also reduce the tank pH.

[seased]

thanks - I will check the pH tonight in the sump. So this buildup should not be occuring in a balanced system?

Prior to using kalk, the tank pH was from 7.7-7.9. After using kalk, it bottoms out at 8.1-8.2 and reaches 8.4-8.5. Concerning aeration, the tank has 2 powerheads on opposing ends and the sump has a Euroreef ES5-3 skimmer. Both the tank and the sump are open. Is this sufficient flow or should I add more water movement? The tank is fairly full of LR with the majority of flow in front of the rock work.

[Randy Holmes-Farley]

So this buildup should not be occuring in a balanced system?

The buildup occurs to some extent in most systems, but having powerheads freeze up in a few months is at the high end.

Total aeration would keep the pH the same day/night. So more aeration will help reduce that high end of pH, but adding vinegar may be easier to accomplish.

[seased]

so the target value for a pH swing should be 1 to 2 points? i.e. 8.1-8.3. Also, pH values above 8.4 will cause faster calcium precipitation on pumps/heaters?

[Randy Holmes-Farley]

I don't think there needs to be a particular target pH swing, as long as it doesn't get outside the optimal pH range. FWIW, mine swings less than 0.1 pH unit.

[seased]

I recalibrated my pH meter last night to make sure it was reading correctly. It needed a little adjustment, but not very much. The pH before lights out was 8.41. The pH this morning was 8.13.

Concerning adding vinegar to the tank, I reread your article on adding vinegar directly to the tank and the other option of adding it to the kalk mixture. If I am going to add directly to the tank, how much do I add? Also, is this something that will need to be done on a regular basis?

As far as adding to the kalk mixture, how much should be added in this method? I'm a little confused going this route, I was under the impression that adding vinegar would increase the amount of calcium that would be added to the tank and it seems that I am currently putting in too much.

[Randy Holmes-Farley]

Yes, adding vinegar is not a one time correction. It effectively adds a burst of CO2 which will reequilibrate fairly rapidly. Maybe start at a couple of teaspoons in a 100 gallon tank, and adjust as necessary.

For the limewater, I'd add 20 mL per gallon of limewater and see what that accomplishes after a few days. Vinegar will only increase the amount of calcium and alkalinity in the limewater if you add more solid lime. If you use the same 2 level teaspoons or less per fresh water gallon, it doesn't appreciably impact calcium and alkalinity .

FWIW, a pH range of 8.13 to 8.41 is perfectly fine, IMO.