pH and algae

[Mitch Rogers]

System is still cycling and  I have an algae bloom and high pH, are these two things related? I don't mind the algae as I had read the forums and it seems that it will clear up after awhile. Im just wondering if there is a link between the 2?

[TCLynx]

yes. 

 

Do a pH test at dawn and another pH test in the late afternoon.  If there is a drastic difference between the two pH tests then there is a good chance the algae is causing the diurnal swings.  The diurnal swings are often because of the algae using up all the dissolved carbon dioxide during the day but at night it will use up dissolved oxygen and give off carbon dioxide.  Carbon dioxide dissolved in water is an acid and will affect the system pH.  If you are having algae like that in your fish tank, you may not want to just leave it.  I generally recommend shading the tank to nearly black out and make sure you have plenty of additional aeration since algae can rob your system of dissolved oxygen during the dark hours.  Algae can also rob the system of dissolved oxygen when it dies and decomposes. 

[Mitch Rogers]

TCLynx - WINNING!

 

thanks once again, sensei

[TCLynx]

Heavy shade for fish tanks is kinda mandatory in my book for most situations.

[Mitch Rogers]

the only reason I hadnt so far is it is still getting a liitle cool at night in north georgia and I wanted some heat to build up in the water during the day. But we're getting up to 70 degrees or so, I may be ok to wrap it now. Do you jusst use a dark colored tarp?

[TCLynx]

I like to use dark fabric so it can still breath and it can still get the benefit of some heating at the same time.

I've got fencing with netting and several layers of shade cloth over my big tank.  The 300 gallon now has a little structure over it with a black curtain on the south side but just netting around the other three sides.

[Mitch Rogers]

ok, that is a good idea. my whole setup is in a small greenhouse, I have even thought about shading part of it this summer when it gets boiling around here. I can already see that my tomatoes will most likely try to shoot straight up through my 6 foot tall greenhouse. the growbeds are already sitting about 20 inches off the ground, then 12 inches of gravel so they only have about 4 feet to grow to a curved top of 6 feet. may be "modifying" the structure haha

[Nate Storey]

UV! UV! UV! UV!  Ok, just kidding, what TC said.  I have used UV, but shading is easier/cheaper. . . getting some nice tannic water also helps. . .

[TCLynx]

UV works too, if you happen to have the equipment (and I would probably recommend the UV clarifier to people using a swimming pool or ornamental water feature that can't be covered up.)

 

Now if you are doing some media bed type aquaponics, once you get the algae to die off and start decomposing down in your gravel, you have a secret weapon to help inhibit algae for a time.  As the algae decomposes it gives off chemicals that do inhibit algae growth.  I believe it is some of the same or similar chemicals that are given off as barley straw decomposes (this is why barley straw is so often used to try to naturally control algae in ornamental ponds.)

 

However, if heavy shading of the fish tank is possible, it will by far be the cheapest method to control algae.

[Mitch Rogers]

Thanks for the good info guys, I am going to try the shading route for now as it is a little cheaper and I think it will be fairly simple to do.  

Nate I looked up tannic water and I am not sure what it does specifically? is it for killing algae or for lowering of the pH?

[TCLynx]

tannins will discolor the water a bit (this happens naturally with a bit of age in an aquaponic system one usually gets a nice yellow/amber tint to the water.)  I don't think this is so much caused intentionally to do anything specific, it is more a sign of things working as they should.  Tannins are generally a bit acidic and the tinting might inhibit algae a little bit but probably not enough to make it worth adding stuff to the water to black it out.  A cap full of maxicrop will give you a nice start on the tining though while not doing any harm and providing some nice potassium and trace elements for the plants.

[Mitch Rogers]

ok cool, My water was a bit yellowish a few days ago but now it is a vibrant green so I think the algae may be a bit out of control, what do you suggest besides the shading? or should I just give that a chance to work?

[TCLynx]

Yep, just black it out as best you can and make sure there is plenty of aeration.