Algae

[TCLynx]

Something that most people with fish tanks exposed to bright light are going to have to deal with is algae. Now if you are talking about a display aquarium or an ornamental fish pond, you may need to resort to chemical or UV means of killing algae along with cleaning it out of the system, however, in an aquaponics system we have to avoid chemical methods and we really don't require the high tech of UV sterilization just to get rid of algae.

There is a really simple method of controlling algae in an aquaponics system, shade any open water from the sun.

Additional benefits of a cover over the fish tank can include keeping leaves and other debris out of the fish tank and depending on cover design, it can also keep fish in the tank if they try to jump out and keep children and pets out of the tank.

Here is an interesting article I once read on algae in ornamental ponds.
http://koiclubsandiego.org/library/green_water.php


Update,
For any of you who think getting the cover over the fish tank is not urgent, think again. Water left uncovered can start growing algae pretty much over night. I noticed this morning that the bins I had been washing gravel in (with system water) yesterday were already turning green this morning. If conditions happen to be right for it, algae can bloom fast and if it happens to be in a system with fish and minimal access to huge amounts of aeration, it could mean fish gasping for air before dawn. So don't wait for the fish tank to start turning green to think about a cover for that tank cause if it starts turning green in the morning, you might not have till the weekend or even the next day to fix it (depending on the fish load and available aeration of course.)
Just your friendly service reminder.

[TCLynx]

Well in flood and drain media beds, the heterotrophic bacteria are not a problem since the flood and drain action ensures there is plenty of aeration for the bio filter. Plus those heterotrophic bacteria break down the solids and make them into more nutrients for the system and along with the worms, they help keep the grow beds from getting totally gunked up with solids so that a properly designed/stocked flood and drain media bed system does not require the grow beds to be cleaned out.

In non-flood and drain type systems, yea heterotrophic bacteria demand lots of dissolved oxygen, however, the only real way to avoid them would be to remove all solids which is not really desirable for most backyard scale systems. Other option is to pump lots and lots of air into the bio-filter to make sure there is enough dissolved oxygen if there seems to be an issue.

[Richard Wyman]

Very interesting. An algae antibiotic. The I have heard Aquaculturists state that the heterotrophs are bad for using too much oxygen and taking too much space in bio filters. He was right, near the end, when he said it raises more questions :)

Seems like some heterotrophic activity could be good in our AP systems. The fact that we rarely exchange water would keep the antibodies ( for lack of a better term ) in the sytem doing their thing. It may also add extra nutrients. Or it may do like the professionals say and just delete too much oxygen.

Thanks for the link TC. Good read.