Diatoms

[MrsHaggis]

Hi Everyone,

My tank has been up and running since December 2009.

A few days ago I started getting diatoms on the sand. I've done a 10% water change and tested my water which is pretty perfect!! I use RO water.

Temp 27oC
Salinity 1.024 (bringing it up to 1.026 slowly)
KH 7
pH 8
Ammonium 0
Nitrites 0.025 (a bit high I know)
Nitrates 0
Phosphate 0
Mag 1180 (also a bit low but not much)
Calcium 420

My lights are on for around 8 hours a day. The bulb was new in December.

The only thing I can think of that has changed is Summer has arrived. The tank is right next to a window and the sun blazes in there in the morning for several hours. Also the temperate outside has gone up by about 20 degrees.

Could that be the cause of these new diatoms?

My algae is under control (thanks to and emerald crab and foxface); my corals are thriving (except the Zoa's are a bit closed today); the fish are fine.

Any ideas?

Thanks
Fiona

[Fish_wiz2]

How old is your tank? If it is mature, then i would suspect the sun. Wiz ;)

[MrsHaggis]

It's been up and running since Dec2009.
I might try shutting the shutters on that window then to see if that helps!

Diatoms are rather ugly and extremely annoying!!!

[Fish_wiz2]

I would try that and look out for your bulbs. 6 months is when i change mine since the spectrum switches around there and i always get cyano and diatoms, and yours is about there... Hope that helps, Wiz ;)

[MrsHaggis]

I asked the lfs about the bulbs and the told me to wait until they are 9 months before changing them!! Not like them not to want my money :O)

[Sugar Magnolia]

If you've not seen any decrease in the diatoms once you remove the direct sun, then change out your bulbs. It may be one, or the other, or a combination of both.

[Fish_wiz2]

I asked the lfs about the bulbs and the told me to wait until they are 9 months before changing them!! Not like them not to want my money :O)

Reasonable store ;) But i've found this by experience, anytime i leave bulbs over 6 month BAM! Algae...

[MrsHaggis]

I'm going to shut the shutters for a few days and see if that helps; the diatoms disappear at night and come back the next day so it's something to do with light (now that I think about it; I'm having a bit of a stupid day today!!).

If that doesn't help then I will get new bulbs.

[Jd205]

Have you tested your r/o water source for silica? or maybe your getting silica from a food or supplement your using?

[stingythingy45]

silicates=diatoms

I suspect your top off water has silicates.
What is the TDS of this water.I find LFS will still sell ro with the tds at or below 8.
And the first thing through is silicates.

[Floowid]

I worked at a LFS and I can tell you from experience, you aren't always getting pure 0TDS RO. Our owner was a bit of a cheapskate and would wait as long as possible before changing the RO membrane. Nobody who comes in for RO water has a TDS meter, so the stores can get away with that for a while.

[MrsHaggis]

I make my own RO water.

My TDS meter registers 5/6 - which after talking to Tunze is fine (spoke to Tunze guy on this site)
I know some people recommend less than 3 but Tunze themselves say anything under 19 or so is fine.