Question about Silica and algae growth.

[krazysvede]

I’ve been battling an outbreak of dark blue/black algae kinda stringy (Cyano?) and diatoms only on my sand bed. I did some testing a couple weeks ago and got readings of 0.25ppm Silica with a RedSea test kit and 0.2 of PO4 with a Hanna Meter. I cut way back on feedings and started running BRS GFO. The diatoms went away but the Cyano didn’t. I’ve siphoned all of it off the sand bed several times, increased flow, and changed all of my RODI cartridges (it was about time to do it anyways) and done 25% water changes a week. No matter what I do the Cyano still comes back really quickly and only on the sand bed.

I’m now getting a reading of 0.04 PO4 on the Hanna (still a little high) and still getting a reading of 0.25ppm for Silica in the tank. So I tested my fresh RODI water and I got a reading of 0.25ppm for Silica, but haven’t had a chance to measure PO4 (my buddy with the Hanna is out of town).

Is Silica fueling the Cyanos growth? If so what can I do to remove it from my water? My RODI obviously isn’t doing anything to help, is there something I can add to it?

Or am I barking up the wrong tree with this and there is something else in my water that’s causing this issue that I need to be looking for? All of my other parameters seem to be in check. The only other observation I have, is that I've noticed that in some areas the algae appears to go away at night with lights out, but then comes back again in the morning.

[Randy Holmes-Farley]

No, silica does not impact cyano at all. It does not use silicate. The reading may also be a baseline error. In any case, I wouldn't worry about it.

If the TDS of the RO/DI water is 0 ppm TDS, silica is not a substantial concern.

[krazysvede]

Well crap! Any ideas of what to test for next that would be fueling such a massive growth of Cyano?

[Randy Holmes-Farley]

Growth of cyano (or any problem algae) can itself reduce nutrients, but intercepting more of the phosphate before the cyano gets it is still a very good plan.

Reducing organics may also help, as cyano can derive energy from organics in the water.

[HighlandReefer]

I have good results when I throughly cleaning the sand bed using siphoning and a proper sized tube which will not take the sand out. This serves to reduce the nutrients escaping from your sand bed which cyano will feed on before you can detect phosphate or nitrate in your water column. If you have not cleaned your sand bed in a while, then perhaps cleaning only about 1/3 at a time may be more approprate. Deep sand beds more than 4" should be excluded from cleaning to the bottom and only the top layer should be cleaned.

[krazysvede]

Ok Ill keep siphoning stuff off and running GFO. Ive already reduced feedings down to what I think I neccesary. Heres a couple pictures to show what im dealing with. This first was yesterday before I siphoned. The second is this morning.

[serval]

krazyvede,
I was fighting something similar and discovered the R/O I had been using was not up to par. I got a new R/O (it wasn't worthwhile just changing filters in this case), a Maxcap R/O DI from Spectrapure, and things are oh so different. This made a huge difference in nutrient levels and algae decline for me. TDS is now zero; things weren't being monitored properly before. Just my experience, it may help you.

[krazysvede]

I live just up the freeway from Spectrapure, I was gonna talk to them and see what they say. I just wanted some advice before I did.

The really really wierd thing is that, when I change water I take old water from my 40 and put a couple gallons in my nano cube and I dont have any of the problems Im having in the nano that I do in the display.... Also, my buddy has the same RODI, its the one Melev has on his site and he isnt having any of the problems I am. We use the same salt mix and only live a few blocks apart, I cant imagine our water chemistry would be hugely different.

[troyman]

diatoms feed on silica ferrous oxide does take out some any of your white phosphate media does a better job i like phosoguard dispite what people say about it leaching alumin into tank i go by seachem they did a study and its not true all meadia puts somthing into water phosogurad stopped my diatom out break havent hadit since and everyone does very well

[HighlandReefer]

krazysvede,

Are you using crushed coral as a substrate?

[Randy Holmes-Farley]

they did a study and its not true all meadia puts somthing into water

I disagree, and have disputed their "study" publicly (assuming it is the same one that I found faulty). I can't find the dispute thread right now, and it may have been in the closed Seachem forum. But IIRC, they did not have the sensitivity to actually detect the released aluminum.

Phosguard also continues to cause problems for folks, probably through by releasing aluminum. Here's a thread from just a few days ago where someone had the classic problem from it (soft corals may close up):

http://www.reefcentral.com/forums/sh....php?t=1805245

[troyman]

mine are fine have no problems maybe adding somthing new to tank who knows i perfer it over ferrous oxide that would leach iron i suppose which to much iron is not a good thing either

[Randy Holmes-Farley]

mine are fine have no problems

That's good to hear. The aluminum problem is not always observed, but often enough to have had folks scratching their heads for 15 years over it.