Crystallization of dosing pump tube

[whitelightning77]

How do you guys avoid getting solidification on the end of your 2 part dosing tubes. It's happening for the most part only on my alk supplement tube.

 

[reef lover]

Myself...i have the tubing from my ato aiming at them to rinse them off. Has worked well.for me.

 

[Crabs McJones]

How do you guys avoid getting solidification on the end of your 2 part dosing tubes. It's happening for the most part only on my alk supplement tube.

How close to the water do you have them? Do you turn your pumps off to feed?do they get any splashing on them? I only ask as I've never personally experienced this and I've been 2 part dosing for quite a while now.

 

[Clownfishy]

I have the same issue and the tube is about 5cm from the service. I have to spray the tube with RO water 3 times a week to prevent this.

 

[Dkeller_nc]

There's several possible explanations for this effect. One is contact with the tank's water or atomized spray from the water. That would cause the buildup of calcium carbonate over time from the reaction of the carbonate/bicarbonate component of the alkalinity reagent and the calcium in the water. Another is simply that the air surrounding the tube is fairly low in humidity, which causes localized evaporation from the alkalinity reagent. Since the alkalinity part of 2-part solutions is somewhat close to the solubility limit, small amounts of evaporation can cause precipitation of sodium carbonate/bicarbonate. Yet a third possibility (though probably an unlikely one) is that the localized temperature of the reagent in the dosing line is somewhat lower than the temperature when the solution was mixed. The solubility limit of carbonate/bicarbonate is temperature dependent, and if one's close to the limit, a small drop in temperature could cause precipitation.

To solve the issue, you'd want to determine whether you actually have precipitated carbonate/bicarbonate, or calcium carbonate. You can determine this by scraping a little of the solid into a small glass container and adding some RODI water. If it dissolves, it's carbonate/bicarbonate salts. If it doesn't, it's calcium carbonate.

If it's calcium carbonate, you'll need to relocate the dosing like so that it's not in contact with tank water splashes or spray. If it's carbonate/bicarbonate salts, then you could correct the issue by decreasing the concentration of the bulk alkalinity part of the 2-part mixtures and increase the volume that's dosed by an equal amount. It may also help to split the amount dosed into smaller, more frequent additions so that the volume of the solution setting at the end of the tube gets replaced more often and doesn't have as much opportunity to evaporate.