Water Glass and Kalkwasser

[clsanchez77]

I have some sponge growth in my tank that has been alive for 5 months now and I am seeing some slow growth, both expansion and new. I feed the tank DT's phyto and oyster eggs. I read some of the chemistry archives that state water glass will provide soluble silica to increase both diatomic algae and sponge growth. My silicates measure around 0.05ppm and I would like to get that up to around 2ppm to see if I have positive effects.

My question is based on that I noticed that water glass has a high pH (pH is 11ish) and was wondering if I could add the water glass to my kalk reactor so that it can be slowly dripped in. The way I would go about would be to figure out the weekly demand and add this amount to my 5 gallon RO/DI reservior. The reservior is fed to my kalk reactor by float switch and aquamedic doser.

So, will this work or will the water glass and kalkwasser interfere with each other.

Thanks,
Chris

[Boomer]

The only possibility is the formation of Calcium silicate. or Silica hydroxide. But I have not checked in to their chemistry much


But these usually requires heat and acidification.

I might add the pH of Kalk is also very high on the order of 12.5. But I do not know what the end result will give. Maybe Randy can shed some light on it for you.

[clsanchez77]

I knew it was high, but was not thinking on the order of 12.5. You would certainly no better than I would ;)

[Randy Holmes-Farley]

I expect you could add it to limewater, but I dose it directly. In this article I show that limewater probably has some silica in it already:

http://www.advancedaquarist.com/issues/may2003/chem.htm

as well as here:

http://www.reefkeeping.com/issues/2003-04/rhf/feature/index.php

[clsanchez77]

Yes, I bookmarked those articles yesterday when researching silicates but have not read them yet. In fact I was going to measure my kalk to see for the fun of it, although I was thinking maybe I need a way of neutralizing it somehow to pH 8 since that would be where the silicate test kit was designed for.

At the same time, given my low silicate readings, I suspect the kalkwasser is not much. I do use a chiller so evaporation is not excessive, I go through about 3-4 gallons a week on a 90 gallon tank and I am thinking of dosing 1mg/l per week, which at 90 gallons, requires me to keep 340mg dosed weekly, so I am thinking of keeping my RO/DI reservior at 20mg/l.

Second question. My tank has an excessively low pH, varies from 7.8 to 8.0 with alkalinity at 3.25meq/l. I have turbulent flow in the tank itself so I know air exchange is good. I live in a condo and unfortunatly, it has bad air exchange, and being a condo, I do not have many options. I allow the kalkwasser to dose 24/7 as needed so its benefit of rasing pH is spread through out the day. I am wondering, would additioanlly dosing water glass help in anyway offsetting the chronic low pH.

Also, separate question, do you prefer dosing kalkwasser 24/7 and allow a pH range of 7.8 to 8.0 or would you prefer dripping kalkwasser only at low pH ranges to keep the range of 7.9 to 8.0. I can not see the upper end of the pH being any different as evaopration and thus the volume of dosed kalkwasser would remain the same.

thanks
Chris

[Randy Holmes-Farley]

The silicate will give a tiny boost to pH when added, but since you will not add very much or very often, it isn't a solution to pH problems.

If dosing limewater only at night will bring up the low pH end, I'd do that.