This is an account of my 6-month long battle with diatomaceous algae — the all-pervading brown monster that has caused more than a few saltwater aquarium hobbyists to throw up their arms in frustration and leave the hobby! My wish is that this article will give hope to anyone battling brown diatomous algae or nuisance algae of any type. Hope, and a Method.

But First, A Little Background
I have been running my 3′ x2′ x2′ saltwater aquarium since April 2006. I started out with a two-and-a half-foot 30 gallon tank in 2005, and for my new ‘big’ tank I transferred all the fish, coral and live rock. I was very carefuI not to overfeed the two fish in my 30 gallon — a yellow-tail damsel and a maroon clown — and experienced no algae problems whatsoever in the year and a half I had it..

Enjoying the increased gallonage of my new, bigger tank I became guilty of overfeeding. I dosed nitrate-inducing supplements like Marc Weiss ComboVital almost daily. My corals and fish seemed to enjoy it immensely. All LPS corals were plump, fat and thriving and tiny coco worms were multiplying everywhere! I figured I had 100 gallons of water and 100 lbs of live rock to handle the nitrate produced with the increased feedings.

I was seriously mistaken. Lesson learned — when in doubt, test for water quality!

Battling The Brown Monster

It all began innocently enough.
Little tufts of brown diatomaceous algae began appearing on the rock. Gradually, and almost unnoticed, they started overtaking and smothering some of my corals. Soon the algae was covering even the pink and purple coralline algae. My tank was in big trouble with no easy solution in sight.

A quick check with the test kit and I found my nitrates had gone through the roof — 100ppm or more. The first thing I had to do was immediately lower my nitrate levels, a fuel for nuisance algae.

I changed 10 gallons of saltwater every 3 days and with each water change I siphoned out as much algae as I could off the rock. They siphoned off the rock easily and I managed to fill entire 5-gallon buckets with the algae that came off.. Unfortunately, they just grew back within 2 days.

My phosphates at this point were reading at 0.03ppm on the test kit. I figured phosphate was being taken up by the algae as fast as it was growing hence the low phosphate reading. I changed the Rowaphos weekly, quickly going through a 500ml can. After the Rowaphos ran out I decided to try out PhosBan, another brand of phosphate removing media, which is finer and more powdery than Rowaphos. The PhosBan tumbled in the fluidized reactor to a fine dust, releasing itself into the sump and up via the return pump into the main display tank. My tank was now looking nice and golden brown! Not a good thing.

And as if to add insult to injury, the algae still wouldn’t budge.

I continued to research the web for answers. I learned that phosphate might indeed be leaching from the live rock, fuelling the algae.

The Brown Monster Retreats
After three months of struggle, with several empty1 litre cans of Rowaphos lining the wall in my fishroom as grim trophies, the tide began to turn. The rocks started to look grey again — the same color the very first day I got them. Small tufts of brown algae remained but they weren’t spreading all over the rock. The fish seemed a lot happier. And once pink coralline algae started appearing in the fifth month I started to replace the corals I had lost.

I began enjoying my tank once again. And gradually, over many months, it came to surpass its previous beauty.

What Did I Learn From All This?

• Prevention is better than the cure. Don’t overfeed the fish and be careful when using coral food supplements
• Water changes are important but not a total remedy in battling nuisance algae. Use water changes as an opportunity to siphon out as much algae as you can
• Phosphate can be bound up in the rocks and leach back into the water over time. Run phosphate remover like Rowaphos from day 1 of your tank’s cycle
• Run phosphate removing media in a phosphate reactor 24/7 and test for phosphate in the water coming out of the reactor so you’ll know when to change the media
• Don’t give up. It is, after all, just algae!