Siphoning a deep sand bed

[Bcb577]

So my wife was trying to be nice and decided to do the water change on my biocube14gallon tank,she said after helping me a col times she knew how and all she asked was for me to mix the new saltwater.I guess I just assumed she was aware of the fact that on my deep sand bed that you shouldn't siphon it.I thought I told her this but she claims I didn't lol.well now after the fact my sand now has brown algae all over it.is this due to the siphoning?I battled dinos and won and was hoping it's the siphoning and not the dinos comming back?any advise or comments welcome!

[Astinus]

Diatoms?

[Bcb577]

That's what it looks like,it goes away when the lights go off but after a col hours after the light goes on it comes back,my parameters all just checkout ok,and I religiously conduct weekly water changes and I don't usually overfeed.I just added some macro algae that's doing fine so hopefully it will consume any extra nutrients?