Silica too low?

Haha... well, we all know that everyone wants to remove silica to stop diatoms from forming... but have we ever thought about adding it back in?

I have a really nice orange colored sponge that has always done really well in my tank. But recently, it started receding, and I think I know why.

In Atlanta, we have really good tap water, around 20-30 TDS is typical. Up until 2 months ago, I never ran a DI, and used an RO system only, and I would get 0-1TDS output. When I found out I could add on a DI for very cheap, I did so, and have been using it with a steady 0 TDS output ever since.

My thinking is that the DI resin is removing the silica and keeping my sponge from forming the spicules it needs to survive.

I am now considering adding it back in... ;D


Has anyone else had experience with this?

Here is an interesting article on Silica by Randy Holmes-Farley: http://advancedaquarist.com/issues/jan2003/feature.htm

 

I have thought about this many times, especially when keeping beautiful sponges like the blues and oranges.

I have also read that even though people associate silica with sand, the actual type of silica that contributes to diatoms is not of the same chemical make up as the silica found in aragonite. Honestly this has been confusing me for years.

With that said sponges always did better for me when some nutrients were present and the water not so polished. They really seem to respond well to stirring the detritus around.

Addition: Just read the link, exactly what I have heard before.

 

I'm thinking of picking up some of this and dosing as Randy suggested:

Tools/Farm*|*Farming*|*Poultry Equipment*|*Water Glass (liquid sodium silicate) - Lehmans.com

 

Probably because aragonite doesn't contain silicates. Aragonite is calcium carbonate.

There is, however, a whole different type of sand, that is made up of silica. That's the typical play sand, but like you said, there's no reactionary path to get that form of silica into a diatom-usable form in our tanks.

It makes sense that sponges do better with nutrients in the system, considering that sponges feed on organisms that would eat silica and other nutrients. They eat bacteria and algae.

 

Yes, Randy Holmes-Farley has a great article on it on the RC archives. I actually purchased some water glass, as per his instructions, and began do dose my tank in very small amounts. I did not notice any diatoms (probably because any that grew were eaten very quickly), nor any harmful effects on my reef. Having said that, I didn't notice any benefits either, and haven't dosed in a while. However, if I was trying to grow sponges, I would definitely begin dosing again.

 

I'm really interested to see if dosing it can help my sponges grow...

Recent evidence has shown that skimmers are very efficient at removing diatoms, and this may be all they are doing... see the recent article here on Dr. Ken S Feldman's research:
Feature Article: Elemental Analysis of Skimmate: What Does a Protein Skimmer Actually Remove from Aquarium Water? | Advanced Aquarist's Online Magazine

I'm also considering silica dosing as a means of nutrient export through the use of the "protein skimmer": Silica Dosing: reef blasphemy or another form of nutrient export?

 

You could probably replace the skimmer in a tank with some sponges, by that logic.

 

I don't think so at all.

The logic is not that sponges are eating up diatoms. It is that they are using silica. So do diatoms. Skimmers remove diatoms, and thus export other nutrients that the diatoms contain.

I never suggested sponges were a form of nutrient export (as diatoms are).

The nitrates and phosphates trapped by diatoms are removed from the system using the skimmer. The limiting factor of diatom growth is not nutrients, but silica.

The same could be said for sponge growth, that their limiting factor is also silica.

I do not think that sponges will consume or filter the water well enough to be considered a replacement for a skimmer.

What I'm proposing (as others have before me) would be to dose silica to increase skimmate production due to the formation of more diatoms, whose previously limiting factor was silica.

 

I was actually suggesting something beyond dosing silica so the skimmer is more effective, as was your idea. I was actually suggesting taking the logic, and food chain, just a step further. Here's my logic:

Sponges may use silica, but they definitely do eat planktonic bacteria and algae. That would include the planktonic diatoms (a type of algae, for those who don't know) mentioned in the skimmer article. I mean, sponges eat things .5 to 50 micrometers in diameter, while diatoms range from 2 to 200 micrometers in diameter. Seems like a perfect match to me.

Their direct use of silica is rather speculative, as preventing diatoms from entering the system completely is rather hard, and then you're not separating the variables in any experiment. However, their consumption of diatoms is rather definitive, which would easily explain why systems dosed with silica have higher success rates with sponges, AND why they have higher amounts of skimmate.

They wouldn't be nutrient export, unless you took out a chunk of the sponge every once in a while. Then, it would be literally nothing different than using chaeto, letting it absorb nutrients (via the diatoms it just ate), instead of directly from the water.

 

I see your point....

I don't think that the small amounts of decorative sponge that we keep in our tanks could filter enough diatoms to put a dent in the system enough to replace a skimmer.

Maybe you're on to something though. Could a VERY large sponge (like bigger than a basketball) filter enough diatoms and produce enough growth to become a viable means of nutrient export or conversion?

First, one would need a very large sponge, and somewhere to put it. You could have a remote sponge "bucket" much like the remote DSB's that some folks use. The cool thing about sponge growth is they don't need light or added energy to grow. I would think we'd be supplementing greater amounts of sodium silicate than Randy suggests in his article, as well. The big thing one would have to worry about is a sudden death of the sponge. We would need to keep an eye on it and be prepared to remove it from the system should it decide to take a turn for the worse.