How to rid your tank of Red-Slime!


The only suggestion I would make is on the water change to rid the tank of red slime. The 10% a month or 5% per wk is good for prevention but once you have the problem a 50% water change is in order.
If your tank has 100gal and 50ppm nitrates, a 10gal water change has the following affect:
This example shows that nitrates are continously it would take over a week to reduce the concentration of pollution in your tank 50% with such small water changes.
This doen't take into account that nitrates are countinuously added to the tank via waste coversion.
You need to do a 50gal. water change to be effective and add a DSB to prevent further nitrate buildup naturally.


Active Member
once you have the problem a 50% water change is in order.
I could't disagree more with this statement. A 50% water change has the potential to wipe out a marine tank entirely. A water change of this proportion on any size tank will significantly reduce the population of denitrifying bacteria which could lead to not only a potential cycle, but furthermore and more importantly an increase in nitrates. In turn leading to more undesired algae/cyanobacteria. This method may work for freshwater, but it is not advised for marine tanks.
This doen't take into account that nitrates are countinuously added to the tank via waste coversion.
Nor does [the example] take into account the fact that in a properly set up marine tank there is an automatic nitrate reduction be it through a dsb, refugium, plenum, or macroalges which expedite the process of nitrate removal. The frequent water changes are not intended to remove the nitrates. That is the function of the removal methods previously mentioned. The frequent water changes are intended more as a method to prevent accumulation.


If the tank chemistry was doing this automatic reduction then the red slime would not be there to start with. If you do the math doing a small water change once the tank is in this condition will not will never catch up. Prevention is the most desired action but once the water gets in this condition you must get a running start toward correcting the problem. If water change is done correctly and water parameters are the same (gravity, temp,cal, alk, ph,) then the large water change will be less harmful than living the nitrates, nitrites, phos, ect at the levels which cause this condition.
I will agree with you that I would not do a water change of this size if I had one small patch of the red devil ...but if it is on the rise and spreading, getting out of control then I would use this method. I have done this three times before when I had tanks that were less than 6mo old and this along with light control has taken care of the problem. Once my reefs were established I have not had to deal with this beast.


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I kicked my cyano in the booty w/ the light method. I went from 12 hours of light to 8 over a 4 night period. I have kept it at that regimen. I syphoned out what I could see of the cyano. I actually got in a debate w/ my BIO instructor last semester about cyano being red. She said cyanobacteria is a blue/green algae. They are always dark blue, green or black. I said out loud that cyanobacteria is also red. She repleied w/ saying that if it's red, it's not cyanobacteria. She didn't even emphisize the difference b/t cyanobacteria and ALGAE. I honstly don't believe she knew what she was trying to teach....Aw man! AND I"M PAYING HER!!:mad: Anyways, I laughed when she asked who told me that. I said " THAT, I knew already, but got to to further educate yourself on this subject." She was snide w/ me, so I returned the attitude. Man Ihope she isn't on this board now.:D


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Cyano is quite easy not to have in my opinion.....although it is sometimes on the rocks....where is it mostly.....on the sand. Why? because the waterflow is too slow, and nutrient pockets have formed. Water changes have zero impact whatsoever since the trouble isn't in the water column. Cyano must reach anaerobic conditions to live, and oxygen is an enemy to it.....tanks with good water flow almost NEVER have cyanobacteria, or any other algaes for that matter.....when I say good.....I don't mean two little powerheads in a 75....that's weak in my opinion. Algae produces waste in the form of hates it would you do in a room full of carbon dioxide? Cyano, ironically, comes in a rainbow of colors.


New Member
Hmm. So that GREEN slimy stuff on my live rock and sand is still "red" algae? I guess then that all the same porceedures above apply, correct?


Ok that was worth the ream of paper to print it. (I've started my own encylopedia of FYI from this message board) on my second 3 ring binder lol ( bump):)


Wow. Thanks for the info Justin.:D I've been battling that nasty stuff for a couple of months and it keeps getting worse. Will try the new ideas soon. Only problem is that there is no room for my tank at my house right now, so my parents are babysitting it. And I can't convince my Mom, no matter how hard I try, that she is overfeeding. Hopefully with your advice I can get rid of this stuff.


Bump for norbert.
Also after rereading this post I wanted to add one thing. From what I've read cyano doesn't actually need nitrates. It's able to use nitrogen directly. So the important nutrient to reduce is phosphate.


absolutely great article. Definately on the top of the longest posts on the site list, since there is a 10K char limit!


just the thing i was getting on here to read about. i will begin trying the various methods beginning with the water changes tomorow!


WOW!!! What a post! And I read every last bit. I'm having a problem with this cyanobacteria... Atleast I think its what I'm having trouble with. This is a brand new tank and its been up and running for a few weeks. But I do admit I leave the lights on from early morning till late at night. And I feed quite a bit 2 times a day. So I now have the lights off, and I'll feed once a day. I'll let you know what happens in the next few days. I hope it goes away a.s.a.p. its so ugly, and there's also little patchs of it on the side glass. I have a 55 gal... how many ph's should I get? Please also tell me where to get them from. Thanks!


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I have a 55 gal... how many ph's should I get? Please also tell me where to get them from.
Can't tell where but 2 or 3 maxi-jet 900 would be good. Try to get a 10x turn over rate for a soft coral tank. Just add the outputs of any pumps (minus head) you have running.
There are some new articles in germany concerning the daily dosing of vodka.
This dosing of C should bring bacteria growth (bacteria plankton) that take up all the NO3 and the PO4, so it can be eaten by corals, sponges,.. or just be skimmed out of the tank.
This is some thing else I read. Hmmm, vodka. And Randy Holmes-Farley writes:
Adding sugar might be a better approach since it is purer than vodka.
When I dosed sugar once, many of my corals turned brown. Probably zooxanthallae growing much faster
One thing to be concerned with is low oxygen as the bacteria use O2 to metabolize the ethanol (or sugar).
In general, growing and harvesting macroalgae is likely to be a better approach.