Milky Silica Solution

Mickey · Mar 4, 2022

@Randy Holmes-Farley - I've been dosing small amounts of silica solution to my 225 gal reef for quite a while now using the Apex DOS (since I had a head not being used). I mix up a 10:1 solution, a liter at a time. The last few months I've seen a lot of white precipitate in the bottom of the container. I just got home from 5 weeks in FL and I notice that in addition to the precipatate, the remaining solution in the container is very milky rather than clear. There's maybe 12 ozs of liquid left. What would cause this? Could it be the colder temperatures in the house? Should I throw it all out and start again with a fresh batch?

I haven't seen any other postings relating to a precipitate in the container.

Thanks.
Mickey

Randy Holmes-Farley · Mar 5, 2022

Is it open to the air for CO2 to enter? That can lower pH and silicate solubility.

Mickey · Mar 5, 2022

It is in a Neptune DDR container made to pair with the DOS. It has a cover on it but is not sealed. Could it be that the sodium silicate settled out and didn't stay mixed with the RO and then precipitated?

I bought it from one of the suppliers you had recommended and then transferred about 1 liter to another bottle (white plastic that originally held a similar solution but more dilute from Florida Aqua Farms). I just poured a little out and that too is milky.

Here's a photo and there's more left in the container than I realized. I may just start over.

Randy Holmes-Farley · Mar 7, 2022

Sodium silicate solution, once dissolved, does not precipitate back out unless something chemical happens. I'm not sure what is happening, but that's a lot of material.

Do you have the original bottle still? Any left in it?

Mickey · Mar 9, 2022

@Randy Holmes-Farley Sorry for delay in responding. I've been dealing with a failed sump pump and a flooded basement.

I checked the original container and there is no sign of any precipitates. A small sample is a bit cloudy but not as milky as what I see in my dosing container. I can't remember now whether the solution was perfectly clear originally or not. Here's a picture if it helps.

Randy Holmes-Farley · Mar 9, 2022

I don't know what happened. maybe it got contaminated somehow.

Mickey · Mar 9, 2022

I guess I'll dump it and start a fresh batch, but smaller this time and see how it goes.

Randy Holmes-Farley · Mar 10, 2022

Let us know what you find.

Mickey · Mar 28, 2022

Update - I haven't been able to get the refills for my Hanna low silica checker. Can't find them anywhere, lots of places show discontinued. Ordered them from Hanna Instr. on 3/4 and nothing yet. I'm waiting for them to give me a new estimated shipping date.

I'm concerned about dosing this without any way to know what my levels are. My Triton test from January shows 1335 ug/l which I believe is 1.335 ppm and I stopped dosing shortly after that because I was concerned about the precipitate.

Since it's been a while I was going to start with 3ml of a 9:1 solution 3 days a week which should give me 18 ml of the silica solution every 10 days and based on @Randy Holmes-Farley dosing recs that should be about 1 ppm SiO2 depending on tank.

Math: paraphrasing the dosing recs.
.96ml SiO2 per 100 gal per week = 1 ppm SiO2
About 200 gal of water need 1.92 ml SiO2 for 1 ppm, round to 2 ml every week or two, assume every 10 days.
20 ml SiO2 (round from 1.92) + 180 ml RODI = 200 ml solution should last me 20-22 weeks at 9 ml per week (I want to dilute the SiO2 but don't want to make too much in case I get all that precipitate again).

Without any testing reagents I hesitate to go higher. Randy - what do you think? Or is it safe to gradually increase until diatoms on the glass get too heavy too fast?