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Gilera

?blue-green algae in brackish tank

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Hi. I recently set up a brackish tank with water from the canal in front of my house. The water is not dirty, it is off the main arm of the Tweed River and very tidal. Twice now I have had the same thing happen. The tank starts out crystal clear once the filter (Eheim classic 350) clears the water initially. Then after about a week, I get this brown stuff taking over the tank. I tried emptying the tank and washing everything and leaving it to dry in the sun for a couple of days but it just came back. The photo below is from about a week ago when it was just starting. Now it is all of the sides as well and makes the tank look filthy. This is only after 2 weeks of setting it up. It has small bubbles when it is in the initial stages so i'm thinking some kind of cyanobacteria? Is this a common battle with a brackish setup? I have read that in freshwater tanks it can be caused by too much light and/or ammonia. I have 2 fluorescent lights over the tank that are on from sunrise to 9pm at night. I do not have many fish in the tank at this stage and don't think I am over feeding. 

Any ideas of what I can do to stop this happening?  

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Hi Gilera,

That's way too much light!    I have heavily planted tanks with CO2 injection and run the lights on a timer for 7 hours per day only.   

I have tropheus tanks where I have the lights on from sunrise until about 7pm because I want to encourage lots of algal growth.  

First thing I'd do is reduce the amount of hours you have your lights on.  

Cheers,
Jason

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Thanks for the advice. Will cut the lights for a few days as advised. When I start them back up again, would going to just one fluoro tube for the same hours provide the same effect of light reduction, or you think better to have less hours in the day with any lights? Our living room is quite a dark room and its hard to see anything in the tank without the lights on (but also hard to see anything when there's brown crap all over everything!). If I need to cut down the hours I will just turn them on later in the afternoon and evening when we are around more to see.

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we run our reef tank on 5-6 hrs a day max, we have the blues coming on at 1300 n white on at 14 n whites off round 19 and blues out at 2000

if i was you i would run a small lamp on it to give u some viewing, and ditch the fluros

 

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All my light timers are set to come on at 1pm and go off at 8pm.

I changed them back to 8pm from 7pm over the Xmas period when we started having a few more visitors around after the COVID crisis of 2020 so you could see the tanks.    

 

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I did as discussed and cut the light down to 1pm - 8pm only. I still have 2 fluoro tubes running during that time. The growth is continuing to get worse - see pics taken yesterday. Do you guys still think it is too much light?

Is there anything else I can do to try to get it under control? I can completely empty the tank again but feel it will likely just happen again. I could replace the sand substrate with something else like shell grit if this might help. I had read a long article about how the depth of sand can affect the difference bacteria which colonise the substrate and can impact on the whole balance. 

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