diotoms after 2 months

[will8]

after upgrading to a bigger tank 2 months ago i am still getting diotoms on my glass and sand. to cycle the new tank i added some sand from the old one which was 4months old. and added 90lbs of live rock and some of the media out of the old filter. i also added one damsel which i had in the old tank.
LFS said i would have to wait 24 hours before added my other fish which was 2 clowns, PBT, coral beauty,
thought everything was ok so i started to add more fish , a flame angel and a royal gramma, checked levels weekly never had a problem with any thing. amnonia 0, nitrites0, nitrates between 15-20, phos 0.1ppm. but still getting diotoms i have been reading alot and what i read is that my tank has not cycled, i change 15% water weelky, but by doing this iam not helping the tank to finsh its cycle?
iam at a total loss with it all, my ca, alk, mag, are all out, been told in another thread to change water but that wont help my cycle.
should say that all my livestock are doing good.
would be very gratefull to any help yet again, before i start to think is it all worth it........

 

[roka64]

If you only have readings of nitrAtes, your cycle should be complete. The diatoms could be from the silicates in your sand. Did you add more sand? If so, how much?

 

[will8]

only sand i added was at the start of the set up of the new tank 2 months ago, none since. the salt i am using is red sea its says it has no silicates in it. so if my tank is cycled what could be causing the diotoms to come back. wiped them off the front glass yesterday and they are coming back already. i have 7 turbo snails and 8 others not sure of their name, they help a little.

 

[roka64]

Are you sure they are diatoms? Usually they will burn them selves out over a few days.

 

[will8]

what else could they be? they are brown, like dust covering the glass and sand.

 

[roka64]

Yep, that sounds like diatoms. Did you add new sand 2 months ago?

 

[will8]

yes added new sand when i set the tank up 2 months ago. is the new sand the problem.

 

[roka64]

It could be the silicates in the new sand. I wouldn't worry too much about it.

 

[cmor1701d]

It's not from the sand. Are you using RODI water? "The most common source of contaminating silicate in aquaria is the freshwater used for top-off or mixing. " That's from Silica Sand by Rob Toonen.

With the parameters you are seeing I agree that the tank is cycled.

 

[Kurt_Nelson]

I think it's just your tank maturing. I still have diatom blooms from time to time, 2 years after I cycled the tank - nothing bad, just a little brown patch on the sand that disappears as quick as it appears. I just take it as a reminder that our little ecosystems are not static things.

 

[melosu58]

My tank is 10 yrs old and I have to run the mag float over the glass to get the dust off the glass. To me you`ll never get over the dusty glass syndrome. Just part of SW aquarium.