Why does Alk cloud when poured?

TylerR · May 30, 2020

When I pour my Alk solution (Reef Fusion) into my tank the mixture makes a brief white cloud. I always thought the cloud was from precipitation (bonding to ca in the water). Sometimes when the conditions are right (High Ca) I can certainly see tons of little chunks and I have no doubt that must be precipitation. But these chunks never dissolve and the cloudy mixture eventually does dissolve so maybe there is some other chemical reaction happening causing the cloud. Anyone know?

MJ in Boise · May 30, 2020

TylerR said:
When I pour my Alk solution (Reef Fusion) into my tank the mixture makes a brief white cloud. I always thought the cloud was from precipitation (bonding to ca in the water). Sometimes when the conditions are right (High Ca) I can certainly see tons of little chunks and I have no doubt that must be precipitation. But these chunks never dissolve and the cloudy mixture eventually does dissolve so maybe there is some other chemical reaction happening causing the cloud. Anyone know?

Ph causes the cloud. Try using double the rodi. I dose 1/2 tsp a day and it will cloud if I use a small amount of water.

TylerR · May 30, 2020

MJ in Boise said:
Ph causes the cloud. Try using double the rodi. I dose 1/2 tsp a day and it will cloud if I use a small amount of water.

But why does Ph cause it? What is happening at the molecular level?

Randy Holmes-Farley · May 30, 2020

High pH additives added to seawater cause transient precipitation of magnesium hydroxide, that will redissolve as it mixes in and the local pH lowers.

I discuss it here:

What is that Precipitate in My Reef Aquarium? by Randy Holmes-Farley - Reefkeeping.com

from it:

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.

Crustaceon · May 30, 2020

This was like chumming the water for Randy.

TylerR · May 30, 2020

Randy Holmes-Farley said:
High pH additives added to seawater cause transient precipitation of magnesium hydroxide, that will redissolve as it mixes in and the local pH lowers.

I discuss it here:

What is that Precipitate in My Reef Aquarium? by Randy Holmes-Farley - Reefkeeping.com

from it:

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.

Oh my god this is exactly what I wanted. Thanks!