Mr. Saltwater Tank

Terrible Advice Tuesdays: No Coraline Algae = Unhealthy Tank

Terrible Advice Tuesdays (T.A.Tues): If your saltwater tank doesn’t have coraline algae growing in it, then your tank isn’t healthy.

The rest of the story: The hunt for coraline algae always amuses me as there are hobbyists who hate it and want it out of their tanks at any costs (*cough* Joe). Then there are the countless emails I get asking how to make coraline algae grow in a tank.

The thing to keep in mind is that if coraline algae isn’t growing in your tank, that doesn’t tell you anything about your tank’s health. I’ve seen countless saltwater tanks all with perfect water parameters, thriving corals and there isn’t any coraline algae in the tank. I’ve also seen tanks that look like toxic waste dumps and coraline algae is happily growing on every surface it can attach.

If you don’t have coraline algae in your tank, getting it grow could be as easy as making sure your magnesium (Mg) and calcium (Ca) levels are in check. Or your tank might not be the coraline algae type for some unknown reason.

Whatever you do, don’t freak out because coraline algae isn’t growing in your tank and certainly don’t reach for a bottle that claims to boost coraline algae growth.

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Comments for this article (8)

  • JasPR says:

    This is such an interesting observation to me! I agree 1000% with the comments. but more interesting is your last comment regarding reaching for a ‘bottle’ of something or the other— HOW confusing this hobby must be for beginners. And ironically, the internet with all its sites, information and “pushers of product” make it all as confusing as its ever been. Its quite natural for the beginner in panic and desperation to begin to mix ‘recipes for success’ from say, a webite of newbies talking to one another with shared guesses, a dealer selling excess inventory about to expire, and a purer source. these things mix in the beginner’s mind and the result is an aquarium in chaos! My point? when it doubt, don’t reach for a bottle ! 90% of the time that will likely be a patch or bandaid to an unlaying issue . In the end, its all about managing things building up, replacing things being exhausted and — the art of balancing a system.

  • mike says:

    Hey Mark. What would be a good calcium supplement to use of I do want coralline algae and how fast can I increase it. My tank is fish only right now and I started with dry reef rock and dry sand. Having a diatom bloom right now.

  • Helen says:

    I don’t have a huge amount of coralline but it could be the six urchins in my tank that have something to do with that! Lol.

  • Tim says:

    I’ve never liked the stuff in my tanks. It looks okay on rocks, but I’m a fanatic about keeping it off the glass and equipment. I think I tank looks “leaner and cleaner” without it.

  • matt says:

    Mark, do you have any information on dinoflagellate algae?

  • jason says:


    Just get your Cal, Alk, and Mg to ~420, ~8-9, and ~1300. (manually dosing 2-part + MG is the easiest way to get it to desired levels)

    After they start to drop a little lime (kalkwasser) in your ATO will keep your levels up.

  • Dee says:

    I got Marks Algae guide and it answers all the questions you guys have above. helped a ton.

  • Thanks for the feedback Dee

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