Algae

Managing Algae

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So you had this pristine white tank with beautiful rock shapes...
and then the green stuff took over.
Yep. That's the way it is.
So let's understand what it is, what causes it, and what you do about it that actually works.
1. What is it?
a) pest microalgaes, green film, hair, bubble.
b) floating and rooted macroalgaes, among them cheatomorpha, halimeda, caulerpa
c) things that only look like algae: cyanobacteria, diatoms

a) and b) depend on phosphate. Eliminate phosphate, and you eliminate these algaes. Should you test for phosphate? Surprisingly, no. Not ordinarily. The test costs money and only tells you what you can see when you look at your tank: you have phosphate if you have a) and b) algaes. If they're growing like crazy, you have a LOT of phosphate.

Where does phosphate get into your tank? 1) sand and rock: it binds with sand and rock, and dissolves into saltwater, so there you are. 2) tapwater: if you're not using ro/di, the stuff is likely not only coming into your tank, it's building up and up, because it doesn't evaporate. 3) fishfood that has algae in it.
To get rid of phosphate: 1) use ro/di exclusively; 2) patience---after it leaches out of your rocks, water changes and especially a fuge will rid you of it. 3) a fuge or GFO (granulated ferric oxide) reactor. You set this up, toss the waste or overgrowth, and you've exported the spare phosphate. Ironically, you can even sell it to another reefer, as algae. BUT: use cheato as your fuge algae, never caulerpa!!!!!!

OK: now to fuges and rooted and non-rooted macroalgaes. Avoid caulerpa like the plague. It's illegal in California, it's killing life in the Med, and it reproduces by 1. runner 2 fragment 3 spores, so it CAN get through your fuge pump; it's poisonous and nasty and most things won't eat it. One fish will: the onespot rabbit, but that fish is large (up to 10 inches) and venomous itself, and rowdy. I really, really advise against caulerpa, no matter how cheap and local. Halimeda is a stony rooted macroalgae: I've never found it to be a problem, except it's persistent and nothing I know eats it. Cheatomorpha is a floating macro that is ideal for a fuge: it reproduces much more slowly than caulerpa, and DOES NOT ROOT in your rock. It also aerates very, very efficiently. I keep my fuge lit 24/7.

Now to NON-ALGAES that look like algaes. The red blush on your sand (brown in some lighting) is cyanobacteria, one of the oldest lifeforms on earth. Look it up. It's a read. To get rid of it, first have a really good skimmer; then turn the lights out on your tank 3 days a month (finish with 1 day of actinic only, if you have MH or high-end LED lighting, total of 4 days.) It won't hurt your reef. But it will kill this stuff, which has only 3 life requirements: water, carbon [which is in all living things], and sunlight. Sunlight is all you can rob it of safely. Since it is also the origin of chloroplasts in all living green plants, forget trying to avoid it getting into your tank---just deal with it as it shows up. And avoid having slanted sunlight hitting your tank: this stuff had its heyday in the era of the Permian Extinction, when weird-spectrum sunlight was getting through the clouds. It loves that situation. Keep sunlight from your tank in all seasons, or expect to have a little of this show up. Do NOT use Red Slime remedy as a beginner: that rides beginner's luck to the max, and you can can crash your tank with it if you make a mistake or if your skimmer isn't what it ought to be. A cyano outbreak is soooo minor, and does no real harm, bad as it looks: don't panic. Take the long route, and you'll beat it within a few months.

And diatoms: animacules, as cyano is sorta plant/sorta animal, this stuff is little microscopic animals. A baby-poop-brown fluff or sheet or stain on the sand. Treat it much the same as cyano, but this stuff DOES like phosphate particularly well, so a fuge will help.