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Black algae ?

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Hello.  this is a 40 gallon breeder that has been set up for 4 months. PH runs between 7.4-7.2; Nitrites 0, Nitrates 0, Ammonia 0.  No C02 just weekly Seachem Flourish; lights on 8 hours a day. Root tabs were placed when plants were planted 4 months ago.  Aquarium houses 13 young emerald corydoras and 2  bolivian rams.  Also a couple of mystery snail 25% to 40% water changes done every 2 weeks. Over the last month black algae (I think) growth noted and yesterday little bits of what looked like white fuzz appeared.  I removed anything that had white fuzz yesterday. Also removed a larger piece of mopani wood yesterday which was covered into another tank with a common pleco who literally overnight cleaned it off. I am trying to understand/figure out what I am dealing with here. What type of algae.  Not sure if black algae because the common pleco loved it.  I was going to try Seachem Flourish Excel but before adding thought I'd ask for advice first.  Thank you in advance. Pictures attached.


algae 1.jpg

algae 2.jpg

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Flourish is not a comprehensive fertilizer and the plants are deteriorating. This allows a multitude of algae to take advantage of favorable conditions. I would look for a comprehensive fertilizer and dose per directions. Give the tank a good cleaning and watch the new growth for any problems.

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Black Beard Algae. Its usually a nutrient imbalance, hard to imagine you have 0 nitrates? You might also consider your tap water a source of phosphates or nitrates. Its an algae thats outcompeting your plants. 

Edit: Didn't see your question about Flourish. Yes, that will work as an algaecide (not really a fertilizer) Though its advertised as a carbon source its main ingredient is gluteraldehyde used widely in the industry to kill algae.  


Edited by ScottieB
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Just a clarification on what @Mmiller2001 and @ScottieB mentioned:

Seachem has a few products called "Flourish".

The "Flourish" and "Flourish Tabs" are fertilisers. But, as @Mmiller2001 mentioned, they are not comprehensive. i find Aquarium Co-Op's Easy Green to be better, and I supplement it with a little Easy Iron, Seachem Potassium, and Seachem Equilibrium.

"Flourish Excel" is the algaecide that @ScottieB is talking about. It is sold as source of carbon, but it's not actually a very good source of carbon.  It is a fairly good algaecide, though.

Considering the condition of your plants at the moment, I'm not sure Flourish Excel is going to do the trick without causing additional plant melt.

I would probably tackle this by heavily cutting back the dying plant matter, dosing with a good combo fertiliser, doing more water changes to keep algae at bay, and letting the plants recover with new growth.

Oh, I would also play with your lighting schedule to reduce daylight period while you get the algae under control and the plants recoup.

4 months is still pretty new, so the tank may still be going through the last bits of cycling. Algae blooms are normal during cycling, but this does look like it got a bit out of control.

This could be due to the imbalance and incompleteness of Flourish ferts with a bit too much light, and a tank that may still be completing its cycle.

Edited by Greg Stewart
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I had issues with black algae until I switched to 2 separate sessions of light per day instead of one long session. My lights are on for 5 hours from 6am to 11 am and then from 4pm to 9pm. The idea here is to give the plants as many hours of light as they can use, but no more, because after that amount of time, the algae can use the light but the plants cannot--they need rest.

Here is a thread about it:


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