Originally Posted by spd0240
I was wondering if anyone can tell me what is going on. I have a 220 gallon tank that has been up now for about 5 weeks. the last couple of days i have been watching this orange brown dusting appear on my rocks and powerheads. What is this and is it good or bad?
Hi Scott, and Welcome to TRT.
I agree that it is probably a diatom bloom that results in new systems from the presence of bioavailable silicates the diatoms use to grow and form their tests. This is a normal step involved in maturation and algal succession in new systems, and can be removed by careful siphoning of the rock and the surface of the sand. This not only removes the unsightly bloom by removing the algae's biomass, but by removing and not replacing the silicates, prevents further blooms of the diatoms from occurring. However, just to make sure, please post some photographs of your rock and substrate that shows us your problem.
Diatoms are growth-limited by the absence of silicates, but diatoms are not the only organisms that use large amounts of silicate in marine environments. The silicates [i]can be sinked by the biomass of forming sponges, which also use silicates to build their spicules, however, this is slow to occur, and sponges may not out-compete some spp. of diatoms for silicates under the right conditions. For now, removal of silicate by diatom biomass removal is your best bet. However, this is an exercise in futility if you continue to replace the silicate by using untreated water to top off or to make ASW: tap water, spring water(in bottles), or any source water from filters that have become unable to filter out dissolved solids. This means only using RO/DI water or distilled water or its equivalents with less than 1 or 2 TDS per volume of water. You can buy this water, but your best most economical means of acquiring this product is to make your own. In this manner, you have total control over the quality of the water, and can assure the quality of your final product through the use of TDS meters. It is also much easier to roll a barrel of RO/DI water on wheels from the location of your filter to the tank and pump it in than it is to lug 5 gallon containers of the stuff from wherever you purchase it.