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I've been reading through the posts but can't find a good general discussion of algae dealing with it in the grow bed itself.  I have a 250 gallon round tank with a liner in it and a square 4x4 growbed covering approximately 4/5 of the top.  I'm going to put a flap on the side to cover the remaining portion. 

I am cycling with catfish and a few crawdad I catch out back of my place and have hard water but otherwise all other things ammonia, nitrates, nitrites and phosphates are within tolerable levels. I'm slowly softening the water so as to acclimate both plants and fish.

In the back corner of the grow bed I piles some oyster shells since i can't access that corner easily and stuck an ornamental water lily back there.  

The systems been running for a couple months and I note that a large amount of of algae is accumulating, on the oyster shells primarily but also on some of the grow media.   Not much in the tank itself just a light film from the low watermark on down.

I've read somewhere that algae is useful in moderation and am wonder if the accumulation mainly in the bed is something that I need to worry about?  Should I drain the bed in between plantings and flush it out? Any input would be appreciated.  I'm still tweaking things and need all the help I can get.

Thanks.

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How do you do your filling/draining in your grow bed?  Do you use a siphon to drain it all out completely on a regular basis or do you maintain a constant water height in the bed?

Hi Patrick..thanks for the question.  I pump it full and drain it on a half hour cycle..leaves it mostly dry for about the last 10-15 minutes of the drain cycle.  I do have a light on at night because of the short days..and that's probably why it's up top.

My question is...will it die on it's own and/or break down and provide any nutrient value?  For some reason it accumulates most heavily on the oyster shells, almost as if they were filtering it.  The do sit at the corner where the fill hose empties into the bed.  Wouldn't be all that difficult to pull them periodically and wash them with a weak bleach solution..rinsing before they go back, if it was necessary. 

Just not sure since there doesn't seem to be much growth in the tank at all and the fish are doing fine.

Aloha Phil

The algae usually doesn't hurt anything, but if it can float free and go "further down the line", you may end up with it hung up on some plant roots. It will clog the plant roots and result in poorer growth than clean roots. Also, if you have any of your system water exposed directly to sunlight (like you described) you're growing algae instead of plants, with the nutrients in your water. Aloha, Tim "The Friendlies" in Hawaii.

Aloha Tim.  Thanks for the insights.  Since I'm still cycling and balancing my system and the levels all come up in tolerable ranges I'm guessing the algae are performing a function by using up "excess" nutrients.  Be an issue when I add more plants and/or fish I guess.  The oyster shells I just used cause I had them but they seem to attract the greatest portion of the algae, acting as a filter almost,  though I've noted some around the sides and on some of the larger grow media in the lowest layer.  but have found only a bit in the screen filter where the water drops back into the FT, so I think I'm good for now.  Only growth in the FT is right a light film of schmutz on the side and bottom at the exposed end and I'm making a flap cover for that to block out the light.

Thanks again.

Are you sure its algae and not green cyano bacteria?

Steve, I have no idea.  guess I have more research to do.  it's definitely a deep green and rather "hairy" in texture.  I perused the discussions a little and found a good cyano site

http://www-cyanosite.bio.purdue.edu/images/images.html

but unfortunately don't have a microscope to contrast it with the various photos there. 

It seems to be confining itself to the grow bed at this point.  Can you school me a bit on the significance of it being one or the other and/or possibly tell me another a way to ID it?

if you're getting algae in your media growbeds, the water level is to high.... the top inch (at least) of the growbed should be dry.. i had this problem for a while until i started distributing the water subsurface... algae will consume the oxygen and nutrients you want to go to your plants

Thanks Keith.  I'm pretty sure at this point it's some kind of algae and you've accurately described the cause.  Have to adjust the system to both add more media and to drain sooner.  Consuming the nutrients doesn't seem to be a problem yet as I have only a few fish and some crawdads on the producing end and few plants on the consumption end.  So in that sense it's keeping the system in balance as my readings are right on target.  But going forward, I'm pretty confident you've hit on the solution.  Thanks again!

Keith Rowan said:

if you're getting algae in your media growbeds, the water level is to high.... the top inch (at least) of the growbed should be dry.. i had this problem for a while until i started distributing the water subsurface... algae will consume the oxygen and nutrients you want to go to your plants

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