Mixing hydroxides as an aiptasia killer

[Gribbles]

I had previously found some posts by folks much smarter than I (@taricha et al) about mixing sodium and potassium calcium hydroxides with water to form a paste. Then put the paste into a syringe and attack the aiptasia. Similar to the product "F Aiptasia".

The problem I'm having is that I've tried mixing this probably a dozen times and only twice have I been able to draw the mixture into a syringe. Every other time I try, the paste almost immediately hardens as I draw it into the syringe. To clarify, the paste in the mixing container is still nice and liquid-like

Why is it hardening so fast and what can I do to prevent it?

 

[redfishbluefish]

This is a @Randy Holmes-Farley question, but my guess is that the mixing of whatever-hydroxide is highly exothermic.....it gets hot. The solubility of whatever-hydroxide increases considerably at higher temperatures. So my guess is that as you draw it into the syringe, it cools, and comes crashing out of solution, precipitating in the syringe.

Let it cool first...and add additional water to keep it in solution.

 

[MarineandReef Jaron]

I have only done this with Kalkwasser as the hydroxide. I dose it any way so I might as well use it. If you haven't tried CaOH then I would give it a go. I have never had any issues with kalkwasser and RO water.

 

[Gribbles]

Oh, I meant to say CaOH (kalk) instead of potassium! I'll edit the main post.

Thank you both!! I had a hunch the temperature was playing a role. I tried to warm up the syringe instead, because I thought I was on a timer before the paste hardens.

 

[Borat]

try 100ml of water, 4g of sodium hydroxide and 4g of kalk. It is not a paste - rather a solution. needs to be shaken before injested by syringe and syringe needs rinsing in ro water after use.

you can make it stronger (maybe 2x) - but there is no need for it for most uses.

 

[Randy Holmes-Farley]

@taricha

 

[Randy Holmes-Farley]

I'm not sure exactly how he arrived at the recipe so let's see what taricha says.

 

[Borat]

I'm not sure exactly how he arrived at the recipe so let's see what taricha says.

this what i have used over many years.. kind of works.

 

[Gribbles]

"Paste" probably wasn't the most accurate adjective. I mix it to a pancake-batter-like consistency. It looks like F Aiptasia and when I can get it into the syringe, it works very well.

 

[taricha]

Here's what Garf and I were doing. If you want something that acts like an F-Aiptasia sort of product (texturally, structurally, encrusting) then you'll want Garf's recipe.

My recipe that I use is much thinner. The resulting solution is anywhere from 2-5M NaOH. 1M NaOH is denser than seawater, but I found I like it more dense than that so it sinks more easily and is harder to blow around. The Ca(OH)2 that I add is a small amount just for texture/ grit - the kalk particulates help the caustic solution stick to slimy tissues better than just NaOH alone. I add 1 red sea scoop of Ca(OH2) per mL of NaOH solution.
here's some of our discussion.

I should probably measure it, instead of eyeballing it tbh. I just dissolve about 1/2 teaspoon of sodium hydroxide granules (caustic soda pearl ) into a small tumbler of water (this gets hot), then use that to make a slurry with a couple of heaped tablespoons of calcium hydroxide powder (and I discard whatever caustic soda solution I don’t use). If you make it too potent or with too low viscosity, excessive magnesium hydroxide is formed when it goes into the saltwater. High viscosity is good (as long as you can get it through a syringe). Altering the viscosity really is just a case of adding more powder or water, it appears the exact amount of sodium hydroxide may have little relevance apart from there being “enough”. You lot have revived my interest in this potention money making method so now I’m playing around with a dry mix of the pearl and calcium hydroxide, so “just add water” lol. I could really do with becoming a millionaire this year, I failed miserably last year (by about a million actually).

My pot and high tech dispensing unit, lol.

I'm sort of on the other end - mostly NaOH with a little Ca(OH)2 just to provide some solids to make it stick better- especially to polyps etc. So it's very thin.
I looked up how concentated the NaOH needs to be to be denser than seawater, and 1 Molar NaOH is 1.04 g/mL which is plenty denser than seawater, so nearly that (or anything stronger) will sink wherever you put it.

Made up a dry mix batch today and it’s 10% caustic soda pearl, ie 5 grams pearl, 50grms calcium hydroxide, add water to required viscosity. Even sticks to vertical glass if there’s a little algae on it for it to bind to.

Running Garf's recipie and figuring out how much water was needed to get the milkshake slurry viscosity I think he's talking about I calculate the NaOH as being in the ballpark of 4-5 molar, pretty similar strength to what I was doing.
I think I like both versions for different things and will keep both in my toolkit.

Garf's "thick version" is Calcium hydroxide with just enough 5 molar NaOH to make it a slurry.
My "thin recipe" is just 5 molar NaOH with a tiny amount of Calcium hydroxide (one red Sea scoop per mL of NaOH) to give it some solids that increases adhering power especially to softies.

Garf's version covers the original surface and leaves behind new Calcified solids (I think what's left behind by the next day is just CaCO3) This version is also good for adhering in vertical situations as he said.


(here it is adhering to a mushroom on vertical glass wall. mushroom was dead/gone a day later.)

My thin version leaves behind essentially no solids, so the substrate is basically reset to bleached rock once the nuisance is gone. I think I'll use this version more often, except when I need more adherence or to bury a surface in new CaCO3 surface.

 

[Garf]

I keep a pot mixed up under the sink, it sits there for months sometimes, just waiting for the call to go and kill something