Precipitation Issue

[Kyle Sicard]

Hey all,
Yesterday I happened to be working under the tank when my dosing pump dosed my alk solution and I noticed instead of the liquid dispersing when it hit the water that it turned into a slurry in my sump. So I'm having a precipitation issue and I'm not sure why. I'm not dosing any calcium currently and my parameters seem to be in check except my alk. Alk: 7.2 DKH, Ca: 450ppm, Mg: 1500 ppm. My alk was 8.6 DKH and last week I muriatic acid bathed my skimmer and I did rinse off all the pieces and the skimmer itself before putting it back in the sump but the next day I tested my alk and it dropped to 6.8 DKH. I figured the muriatic acid residue dropped the alk so i adjusted my alk doser to add additional alk for a slow increase back to normal levels. I checked 3 days later and my alk still read 8.6 DKH. I thought it was odd but increased the dosing anyways, then today I noticed the slurry so I'm assuming its been precipitating this whole time.

Does anyone have any advice on how to correct this issue? I'm dosing way more then usual and have only gotten my alk to 7.2 DKH. I don't want to dump a bunch of alk solution into the tank so if anyone can advise me on how to get the precipitation to stop I would appreciate it.

 

[Randy Holmes-Farley Verified Community Expert]

It is normal for sodium carbonate and calcium hydroxide solutions to form a temporary precipitate when hitting the tank water. The precipitate is magnesium hydroxide, at least initially. It will redissolve as the local pH returns to more normal levels as it mixes in.

You do not want the solids to sit around without mixing in as local precipitation of calcium carbonate (a slower process) will begin to become significant and it won't redissolve.

Try adding to a higher flow/high turbulence area so the dosed solution mixes in and redissolves more rapidly. Adding more slowly and diluting more before dosing can also help.

This has more:

What is that Precipitate in My Reef Aquarium? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2005-07/rhf/index.htm

Figure 3. The transient cloud of magnesium hydroxide that forms when high pH additives are added. In this case, the alkalinity portion of B-ionic was added to a fairly still portion of one of my reef aquaria.

 

[Kyle Sicard]

I don't believe what that picture shows is whats happening. That's how it normally looks when the pump doses. What I saw yesterday looked like snowflakes/flurry, definitely not a cloud like appearance. You could see all the white particles separating and just floating around.

As soon as the solution hit the water it turned to slush instead of the normal (AKA what the picture shows).

 

[Randy Holmes-Farley Verified Community Expert]

I don't believe what that picture shows is whats happening. That's how it normally looks when the pump doses. What I saw yesterday looked like snowflakes/flurry, definitely not a cloud like appearance. You could see all the white particles separating and just floating around.

That might be the same in a larger crystal form, or it might be calcium carbonate. In either case, the ways to reduce it are similar.

If you switch to baking soda (sodium bicarbonate) instead of sodium carbonate, it should not form.

 

[chickenreef]

Mine does the same, looks like little snowflakes but it dissolves before it hits my return chamber.

 

[Kyle Sicard]

Thanks for the reassurance, I just wanted to make sure nothing funky was going on. I'll probably switch to the baking soda once I run through my current batch of soda ash.