Mr. Saltwater Tank

Terrible Advice Tuesdays: Windows = Algae Outbreak

Terrible Advice Tuesdays: Placing a saltwater tank near a window means you’ll have algae outbreaks.

The rest of the story: Old wife’s tale, Terrible Advice Tuesdays. Terrible Advice Tuesdays, meet old wife’s tale. As explained in the algae guide, if you have an algae problem, you have a nutrient problem. Adding light to the equation, no matter what the light source, gives algae nearly all it needs to start growing.

If you have an algae problem, don’t blame your window, blame the nutrients.

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Comments for this article (17)

  • Christopher says:

    So I’ve kept up with water changes and I lightly feed as to not have any leftovers and the tester shows really good results on all my levels except hardness. Yet this purple algae starts I form on the sand like a cobweb and will not stay gone. It eventually forms longer hairs but for the most part is a thin blanket. I would not say nutrient problems in this case. What could it be and how could I get rid of it permanently? I did cut back the light but it only slows it down. Anymore and I’m afraid for the coral.

  • Jim says:

    You know Mark if people actually read your books instead of just taking what is said on forums etc. as the whole truth and nothing but the truth they would be better off, I am not saying that all forums advice is wrong but just check it out with other people read a book and then make your choice before you make big $$$$ mistakes.

    read read read my son and you will have knowledge beyond your belief

  • John says:

    Mark, agree 100%. I have all your guides and your advice is right on. My tank gets some early morning sun. Never had a algae problem. I feed my fish only once a day. If the food hits the sand I am feeding to fast. I never feed more than two minutes (your suggested starting point). Fish will alway eat….they are not smart enough to realize this will not be their final supper. I never feed my corals or add any add any additional foods. Full reef with SPS/LPS/Softies and everything grows like weeds without supplements. Everytime a reefer buddy has a algae problem I nearly faint when they tell me how much they feed and all the nutrients they are adding. Algae in your tanks? Three days of darkness and stop dumping nutrients in your tank is just what the doctor ordered.

  • Richard says:

    Mark there may be a miss match. My e-mail mentioned damsel fish and tank cycling, not algae & windows. I just clicked on the lower “”See the terrible advice” url on my email invitation and got here. Its okay, all terrific advice, but I wanted you to know.
    Thanks for all you do.


  • Christopher says:

    I feed sparingly and once a day as well. I learned controlling the food controls the algae. Only in this case, purple for some reason, will no go away and all my levels look great. I’m hearing rumors that this purple algae is an epidemic in regions but know nothing of he truth. So you’re sayin to do what I’ve been doing and problem isn’t solved. I tried the no light for 3 days and it cleared up only to come back. None of my cleaners are eating it either. No problems with green algae. Tank looks very clean otherwise.

  • Christopher says:

    Same thing here, mismatch. And I did read marks first book btw

  • JasPR says:

    O the innocent arrogance of youth! 😉 before I turn off 80% of the readership, please read a little more— I’m not talking about chronological age but ‘age’ in the hobby. we are ALL subject to the culture of our times. And the process of innovation and imitate ( please read ” improve via variation”) is the evolution of our hobby. But ‘youth’ tends to believe that now that I’ve arrived, all the past is meaningless. I assure you, in twenty years many newbies will be laughing at when we believed in back in 2014!
    The old timers are actually right but maybe not for the reasons they believed. now I get that one grain of truth tends to throw babies of old out with the bathwater– don’t introduce disease! don’t risk the living when chemistry can be accomplishes INORGANICALLY! But here’s the rub– you can’t fool mother nature. Even in our ‘closed boxes’ mimicking nature, you still can not fool mother nature. If you go the bottled product root as an enlightened version of the hobby, do realize that your system is both supported by and eventually distorted by organic material. And it is this matter that ‘feeds the system’ and guarantees what will grow and not grow– so the idea is to keep your system ‘desert like’ in nutrient but enough to accomplish two things:
    1) deal with inevitable organic build up so as to keep base line readings unmeasurable
    2) recognize that if you attempt to remove all organic compounds to true zero your will have a very ‘near the edge’ and unstable environment

    This is because mother nature abhors a vacuum and WILL attempt to fill niches with back ground exploitive species. These species of heterotrophic bacteria, slime bacteria, single cell algae, protozoa are masters at mass reproduction/replication. So to deny that a system which was established without organics can, at a point, fend off species that wait for the inevitable presence of organics — is well— child-like thinking.
    Nope, damsels are a good start towards the realities that will be present in your system upon the addition of your very first fish purchases. You can’t follow mother nature. JasPR

  • Laurie says:

    Hi Mark
    I am not receiving any alerts about your Monday Lunchtime online chat anymore, have these discussions stopped to give you more time with your new baby, or is there another reason why I am not getting them.
    you are greatly missed. thanks

  • Laurie…I haven’t been doing the Midday Monday Q&A over the summer. I might start them again in the fall

  • cheryl boggs says:

    JasPR, again you pretty much hit the nail on the head. As mere human, some of us work really hard to replica what we pretty much will not every achieve. Water in the oceans, etc. Good. In a closed box lets just say, some very good considering, good at best, and maybe I should just give up, for some. You just have to love this hobby and just do the best that you can do.

  • Mike says:

    Christopher what you are describing sounds very much like cynobacteria. You probably started with Diatoms–Golden brown all over your rocks. You are not in a cynobacteria stage, and most likely will see that fade to be replaced with Green Hair Algea.

    I have been fighting this problem for about 1 year now. My tank is 17 months old. I have heard both sides of the story on what causes this. Algea needs three things to live. Light, nutients, and water. You may have very good readings for Nitrite, Nitrate and phosphate and still have an algea problem. The readings a scewed by the algea, the nutrients are being locked up in the algea and hence the water readings appear very good.

    Continue with water changes, monitor the food source–look for phosphates and realize that algea grows in every enviroment on earth.

    Good luck!

  • Mike says:

    Sorry, ment to say “now” instead of “not” in third sentence.

  • beth says:

    Christopher and Mike, if you have cyano then you have a bacterial infection in your tank. Nothing to do with parameters, your tank has an illness. The best way I have found to beat cyano is with Dr.Tims Re-Fresh followed several days later with a dose of Waste Away. Many will tell you to use an antibiotic called Chemi-Clean, I try to avoid that because in killing the cyano bacteria it also will kill the good bacteria. I swear by Dr.Tims for keeping the good bacteria plentiful and therefore out doing the bad bacteria. Hope this helps.

  • Christopher says:

    Thanks mike for the advice, will keep up the routine and see what happens. Maybe I can return to normal lighting cycles and have the algae eat itself to death lol

  • Gary says:

    Hi Mark,

    Just to echo Laurie’s comments – you’re greatly missed. Hope to see the Monday Q & A sessions up-and-running again in the autumn.

  • Ashton says:

    Mr. Saltwater tank,
    Quick question, why aren’t you on Instagram? It’s all pictures…let’s face it..we all love pictures. Only asking because I’m not on Facebook or Twitter. Thanks mark

  • Merle says:

    Hi Mark,
    Another question: Since start up almost 3 years ago I have had issues with Diatoms.
    I use RO/DI for changes and my ATO. I’ve tried different vendors and no change. The least trouble I had was using distilled but, while not as bad was still there. I removed my sand bed and replaced it with crushed coral. It’s only been a week and the coral is being covered. Any advice?

Comments are closed.