Silicates in RO Water?

Paul Taylor

Paul Taylor

New Member
Hi all,

My tank is in the early stages (just over two months running, it is cycled, and now has only 2 clownfish) and a diatom outbreak started within a week of adding the fish. This is normal I understand and I resolved to be patient and wait for the diatom's food source (silicates) to be exhausted and the diatoms to die out naturally.

However, I noticed immediately after a water change the diatoms outbreak multiplied significantly, covering all the glass of the tank, the sand and the rock (which had previously been cleaned by the snails). It literally went from a mild covering on the sand to the entire tank being completely covered overnight.

This led me to order in a test kit for SiO2 to test for silicates in the salt water I used to top up the tank (I still have some left).

SiO2 in the display tank currently: < 0.1 ppm (6 days since w/c)
SiO2 in the left-over S/W mix I used for the water change: 1.6 to 2.0 ppm

As this is in a new mixing barrel I have just bought, I also thought to test the 'pure' RO that I obtained from my LFS both barrels are also showing 1.6 ppm to 2.0 ppm SiO2.

Could this be a problem with the LFS RO water?

Or the two barrels I use to carry it back from the shop? (Both were bought from the LFS and they may or may not have been new at the time as they also rent out these barrels).

I presume I am never going to get through the outbreak if I am constantly adding food for the diatoms?


Any advice/suggestions would be appreciated.
 
Luukosian

Luukosian

Well-Known Member
Really only way to control your water quality is to get your own ro/di unit and I'm sure that's what others on here will tell you as well. The units are relatively cheap and it beats lugging water back and forth from the lfs. If you still want to buy their water the only way to know is just have them pull some for you and put it in a different container and measure. If you are constantly adding 2ppm silica back to the tank you are going to keep having a problem. Gotta think, not only are you adding 2ppm silica water when you do water changes, every time you top off you are adding more silica(and not to mention what else might be in there).

We buy all the expensive salts, test kits, livestock, and equipment....I don't think I'd risk it all on mystery water even if silicates weren't an issue.
 
Paul Taylor

Paul Taylor

New Member
I originally started using their RO water for my freshwater tank when I figured out that our local tap water was very high in Nitrates (and presumably phosphates and lord knows what else) so my water changes were topping up not diluting! So my main concern for their water at the time was for Nitrates equalling zero, which they did (and still do even in this current batch), but I've just read something about silicate scaling on RO membranes, so perhaps they are not keeping up with their maintenance?

The main reason I've kept going back for it from the shop rather than having my own unit is not cost, but rather where/how to install it. I kind of assumed you'd need a permanent setup with a barrel constantly attached to it, as that seems to be what I've seen on most videos etc. Seems I may be wrong on that front. If it can be setup in such a way I can just plug a barrel into it for as long as it takes to make up a batch of water it might be more feasible for me to find a way to do it. Bearing in mind it needs the Mrs' approval, although she can't stand the dirty brown 'diatom' coloured tank we currently have I may have a valid argument.
 
Last edited:
Paul Taylor

Paul Taylor

New Member
I will look into the option of my own unit further, but I'll still raise the issue with the LFS tomorrow and get their water re-tested in any case. Thanks for your help Luukosian. :)
 
Luukosian

Luukosian

Well-Known Member
There are plenty of options for installation, most units are pretty small(like underneath the kitchen sink small). I only run mine on-demand when I need water. You can just use a vampire tap which can be installed w out messing w any plumbing then drill a small hole and silicon it shut for the drain line. It's relatively easy but if cost isn't an issue and you're not comfortable with it just hire a plumber to plumb it in more permanently. Then you can just roll up a container on wheels or run the line long enough to where you want to fill up water.
 
D

DaveK

Well-Known Member
Paul Taylor said:
...

This led me to order in a test kit for SiO2 to test for silicates in the salt water I used to top up the tank (I still have some left).

SiO2 in the display tank currently: < 0.1 ppm (6 days since w/c)
SiO2 in the left-over S/W mix I used for the water change: 1.6 to 2.0 ppm

As this is in a new mixing barrel I have just bought, I also thought to test the 'pure' RO that I obtained from my LFS both barrels are also showing 1.6 ppm to 2.0 ppm SiO2.

Could this be a problem with the LFS RO water?

...
Click to expand...

Yes, this can very much be the case. Most RO units by themselves do not do a very good job removing silicates. Typically for most other items in the water you can expect an RO unit to remove abou 99% or more. For silicates typically it will only remove about 50% or so.

The solution is getting your own RO/DI unit. The DI section will take care of the silicates that the RO section misses.

There are also RO membrane filters available that can remove a higher percentage of silicates. Here are a couple of them (offsite) -
http://www.marinedepot.com/Captive_...Captive_Purity-CP1811-FIRORPRO-CP1821-vi.html
http://www.marinedepot.com/Kent_Mar...es-Kent_Marine-KM2241-FIRORPRO-KM2243-vi.html
 
Paul Taylor

Paul Taylor

New Member
DaveK said:
Yes, this can very much be the case. Most RO units by themselves do not do a very good job removing silicates. Typically for most other items in the water you can expect an RO unit to remove abou 99% or more. For silicates typically it will only remove about 50% or so.

The solution is getting your own RO/DI unit. The DI section will take care of the silicates that the RO section misses.

There are also RO membrane filters available that can remove a higher percentage of silicates. Here are a couple of them (offsite) -
http://www.marinedepot.com/Captive_...Captive_Purity-CP1811-FIRORPRO-CP1821-vi.html
http://www.marinedepot.com/Kent_Mar...es-Kent_Marine-KM2241-FIRORPRO-KM2243-vi.html
Click to expand...

You know, I kind of assumed when I was getting 'RO water' from the LFS, it was actually a short version of 'RO/DI water' and I though that was what I was getting! I guess the old saying about 'assume' applies here. Will still discuss it with LFS though as they have some fine looking tanks.

I am in the UK though, so I'd prefer to find a decent product and supplier locally if I can (mostly due to shipping issues).
 
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