Greenwater Aquaculture

[Pugo]

Algae is not your friend in Aquaponics, We spend a great deal of time trying to keep algae from growing in the system, there is enough of a problem dealing with Bio-film. I noticed a protein skimmer in that video to, something else you really don't need. Greenwater systems always have a DO problem which leaves you with a lot issues depending on your fish density and the size of your ponds.

[greenfish]

Im pretty sure that the filter in the link i provided is not hooked up to either a RAS or a aquaponic system, it just showed the hanging screens.

The algae would be used in an RAS to remove nitrates.

[Pugo]

It appears to be setup for an aquarium inside of a house and judging by the kind of protein skimmer that was employed it would a saltwater system. But just a guess on my part.. it very well could be setup for freshwater but the setup would be very serious over kill for freshwater.

[greenfish]

Well, your guess is better then ten of mine. I just used the video as an example for how they intentionally grow algae, just like you would in a greenwater aquaculture system. Should this thread be in the aquaculture section?

And as for the DO problem, what does anybody think about being able to remove the algae during the night by simply stopping the pump from feeding the algae constantly. Maybe put it on timer to keep it moist. You would need to have it on a separate pump and I know greenwater systems are supposed to be low energy. But, if you didnt feed the fish too late and the pump only needs to be off for acouple hours, maybe it would be alright to have just one pump. I wonder if the algae would be able to breath enough to survive the night?

Feel free to just say shut up and its a stupid idea.

Greenfish

[GaryD]

Hi Greenfish,

Algae is central to the functioning of a greenwater system. The algae, coupled with other organisms that it attracts, is largely what feeds the fish in the system.

Greenwater culture is not generally associated with aquaponics as such. It's a relatively low tech approach to fish raising that relies on the algae to manage water quality.

Gary

[velacreations]

I keep coming back to this concept from an energy point of view. Going back over all the greenwater documents I can find, I am seeing some promising things for a low energy system.

Let's look at an example 8000L system
pump 1200 LPH (5 watt airlift)
turns over tank volume every 7 hours (several times more than the UVI systems)
400L clarifier - 2X 200L drums, remove sludge daily
4 airstones with 5 watt air pump
final stocking rate - 10kg/m3 (possibly up to 15 kg/m3)
number of fish - 160 grown to 500g, 80kg harvest
solar system - 40 watts, with battery enough for 5 cloudy days - $400

So, now you are looking at 160kg of fish a year or running a continuous system with an average stocking of 10kg/m3, which should produce even more (above 200kg/yr). All for 10 watts. This seems really efficient in terms of energy.

Does anyone else have thoughts on the energy side of this?

[Ravnis]

It's way more energy efficient than an aquaponics system, but you lose the plant growth in the system, so overall efficiency is lower. The solids that are removed can be added to a different type of growing system though, but this would involve manual labor inputs. Basically you trade electrical energy for mechanical energy typically provided by humans.

Another requirement is a growing area that does not get too cold as heating would defeat the purpose of a low energy system.

It is a cheaper way to get started in growing fish as fish food is optional if growing a fish that eats algae.

[velacreations]

do those numbers look something similar to your system, Ravnis? Do you have 4 air pumps for your 6,000 gallons?

What other fish might be suitable, beyond Tilapia?

[Ravnis]

I'm sorry I don't have any hard numbers. When I moved them indoors I had ~300 lbs of fish in the 5000 - 6000 gallons of pool. I was using 2 air pumps that are rated at 5 watts and 9 liters/ minute. I had also given 50 lbs of fish to a friend to start his system with. The air pumps were not sufficient and I should have used 4 at least.

Are you wanting to grow veggies too? If so you are better off with the aquaponic system you had laid out.

[velacreations]

well, I have lots of wicking beds, so I was thinking of pulling water off a system for them. I am more interested in spending the energy to grow fish, cause I can grow plants without any electricity already.

The aeration part is the wild card, here. Even UVI doesn't mention what was required in their test setups. They mention the amount of airstones, but not the airflow or wattage of their blowers. So, it is difficult to estimate what is possible.

Did you have a lot of baby tilapia born in the system? Will you be doing something similar in the future?

Ok, so based on what you said, maybe cut the volume in half for the 10 watts. So, like 4000L with the 2 air pumps. That'd be about 80 fish in 1000 gallons. That's around 80kg per year for 10 watts. Not too bad. If you did a continuous harvest method, you could probably harvest up to 150 kg a year.

I think that's going to be more efficient than the RAS or AP setup. Focusing the energy on aeration, rather than pumping, helps on the energy side of things. This has a lower stocking rate than an AP or RAS (for the same energy level), but it has 3 times the water volume for the same energy, so you end up with more fish.

I wonder if an RBC like Cecil's could be used to help with aeration: http://www.aquaponicshq.com/forums/s...I-put-together
It seems like you get extra aeration with that for the same water flow, but the algae might be an issue with it.

What I really need to do is setup a greenwater system and a RAS, and run both on 10 watts, and see where the limits of each system is.