[Canadian]

You know, I can certainly appreciate that generally the cause of hair algae is excess nutrients. And that typically the excess nutrients are caused by some poor husbandry.

However, people seem to be really quick to attribute the problem to someone's husbandry without getting all the information.

I find the most often misdiagnosed cause of hair algae is poor liverock. Over the last 10 years liverock has become more and more poor in quality. Additionally, LFSs generally have really poor "curing" practices. Liverock is tossed in a vat with some meagre flow and everything on the rock decays and clogs up the liverock. So most hobbyists are buying nice, big, expensive chunks of phosphate to start out their reef tank - great start! Unfortunately, most newbies don't read about "cooking" and despite great husbandry practices and top notch equipment they find themselves battling hair algae in short order.

When the problem becomes too much to bear, they post online after numerous failed attempts to get the problem under control. Inevitably they post that their test kits read zero phosphate and zero nitrate. They might even be astute enough to observe (if they have them) that their SPS are rather pale in coloration. Then some "well intentioned" hobbyist suggests they have to have phosphate and nitrate or the algae wouldn't be growing - "it's just being pulled out of the water by the algae so your test kit can't read it" or "your [insert brand/type of test kit] isn't very good and isn't capable of reading values below x".

With this phosphate laden liverock remaining in their tank they're going to fight a long, arduous battle. The phosphate is slowly leaching out, and you'll often see detritus being expelled from the liverock just like you would see in a vat with "cooking liverock". Unfortunately the tank is well lit and there's already hair algae there so it traps the organics being purged from the liverock and continues to fuel the algae's growth without it ever making its way into the water column. This can go on for years and all the while you'll test your water and continue to be befuddled by the fact that you're adhering to every good husbandry practice under the sun with no measurable phosphate or nitrate and yet this insidious hair algae continues to grow while your corals suffer from a lack of nutrients.

The take home message: Start with clean liverock. And if all else fails to correct the problem should you have started your reef tank with yucky liverock, start again with clean liverock. We, myself included, far too readily accept paying thousands of dollars for equipment and carefully planning out our equipment layout and design and then go on, without so much as a second thought, to just purchase whatever liverock is readily available and toss it in our "kinda well thought out tanks" only to become frustrated.