Fish sediment

[urbanfarmer]

It's a difficult issue to discuss because of the contradicting view despite basic scientific principles. To be honest, the issue has not even been settled here on this forum between the members, and I have not been inclined to put together the information required to settle the matter. I don't use air bubbles in my system and there are no signs from the organisms I am cultivating that I need to. With that said, an air bubbler is just fine for your setup. You can't HURT anything (besides your wallet) by buying equipment for the system to add oxygen.

Short answer: Yes, there's a better way. No, you don't need to know about it right now.

[rfeiller]

you can create a current with the air stones, a power head a submersible pump.
an air stone will live the water and draw water to it, a submersible pump will do the same thing.
if you place an uptake at one end and push the water from the other end you will create a current that will carry the sediment to the uptake. as jackalope was discribing

i maintain air stones in all of my tanks to circulate the water. it prevents zoning of the water, temperature and oxygen dispersement.

[urbanfarmer]

Do you have data to indicate the rate of diffusion of oxygen in water or aqueous solutions is slow enough to create "zones" in your water column that are low enough to kill your crop or reduce your yields? It seems counter-intuitive to me. I ask you, please heavily question your assumptions.

4 ppm (4 mg L^-1) of dissolved oxygen is recommended by Dr. Wilson Lennard; however, scientific research clearly shows that fish like Tilapia are capable of surviving and growing in waters with less than 1 ppm DO levels. Depending on the temperature, most backyard systems will not drop below 2 ppm DO, and usually not below 4 ppm DO. Unless you are running a high density fish stocking regime in a commercial environment, why the heck would you even bother making your system more complicated, more costly to build, and more costly to maintain? Aquaponics as a solution for world hunger would dictate that poor folks in 3rd world countries would neither have access to or the means to add this kind of equipment, yet many organizations are designing systems that work for them. Rightly so! I understand wanting to have the BIGGEST, SHINIEST, and MOST EXPENSIVE system, but it's just not needed. Please be sure to indicate to people that you add all the fancy bells and whistles because YOU WANT to NOT BECAUSE THEY HAVE TO.

With that said, there are SO many factors that can contribute to the overall performance of your system. Understanding the science and technologies involved will allow a person to troubleshoot or diagnose specific problems to their very unique system and production goals. I can easily give you a context where the information below would really not help, but I think it puts my point on dissolved oxygen into perspective.

Several tilapias are reported to tolerate oxygen levels of 0.1 – 0.5 mg/l (O. mossambicus, 0.1 mg/l, Maruyama, 1958; O. niloticus, Magid and Babiker, 1975; O. mossambicus 0.4 mg/l at 30C and 0.6 mg/l at 35C in closed respirometers - Mohammed and Kutty, 1982; Tilapia guineensis and Sarotherodon melanotheron and O. niloticus - nil oxygen, water depleted of oxygen by a addition of tobacco waste in low concentrations, but fish allowed access to air - Kutty, unpublished).


REFERENCES
Magid, A. and M. M. Babiker. 1975. Oxygen consumption and respiratory behaviour of three Nile fishes. Hydrobiologia. 46 : 359 – 367.

Maruyama T., 1958. An observation on Tilapia mossambica in ponds referring to the diurnal movement with temperature change. Bulletin of the Freshwater Fisheries Research Laboratory, Tokyo . 26(1): 11-19.

Mohamed, M. P. and M. N. Kutty. 1987. Observations on low ambient oxygen tolerance in some freshwater teleosts. Experimentia, 129 – 138.

[keith_r]

so if you look long enough you can find fish that can live in low do.. but why would you want to set up something that isn't going to have best performance? just because a fish will "survive" at minimal levels, doesn't mean you'll get the best growth of the fish! (or the plants for that matter)

[urbanfarmer]

I didn't see if the study discussed the fish growth. I think in general everyone disregards the fact that there is another factor at play... the air around us. The reason those fish survived is because of the air. Plants in rafts or gravel grow beds that drain have roots and bacteria exposed directly to air. It reallly, REALLY, depends on how you have your system set up and if you took into consideration different factors when you built it. Most backyard aquaponicists do not need to add aerators to their systems.

Just like we graduated to the concept of using 1 pump instead of 10 in our systems, we need to learn to not use any aerators.

[cedarswamp]

How are the folks in the 3rd world pumping water?

IMHO aeration gives you a little wiggle room to compensate for our human error/neglect. I've never run a fish tank without also running aeration. To paraphrase/quote? Dr. Wilson Lennard, "Take care of the fish and the plants will take care of themselves."

While fish may adapt to lower levels of DO, the stress it may cause IMHO invites disease/pathogens.

[davidstcldfl]

It really, REALLY, depends on how you have your system set up and if you took into consideration different factors when you built it.

Nothing like a good diy spray bar or a venturri...

Most backyard aquaponicists do not need to add aerators to their systems.

That's true in 'some' cases. If I were to make such a broad statement, I'd be more inclined to say something like.....'Most' backyard Aper's are stocking too many fish and 'need' to run an aerator.



I agree with Ceadarswamp. "Wiggle room'' is key to a succesful operation.
Redundancy is our friend. 2 smaller pumps working together, on separate circuits....toss in an air pump and you have the old "Three folded cord'' thing going on. Even in a backyard set up, that's not really out of the question. Compared to the possible loss of fish and the frustration factor.

[urbanfarmer]

Nothing like a good diy spray bar or a venturri...

I couldn't agree more!!!

Most backyard aquaponicists do not need to add aerators to their systems.

That's true in 'some' cases. If I were to make such a broad statement, I'd be more inclined to say something like.....'Most' backyard Aper's are stocking too many fish and 'need' to run an aerator.

Well, I said most because I don't think the majority have a high stocking density... but yes I don't have true statistics to back that statement. I guess I should have said:

Most backyard aquaponicists have the space and resources to create enough water volume and tank surface area to prevent the need for added aerators and should use in lieu of such equipment the return water flow as a source of surface agitation for gas exchange and aeration. Happy now, sir??

[badflash]

As long as the pump keeps running, you don't need bubbles. If the pump stops the bubbles buy you lots of time to fix it. Making bubbles costs very little in power or material and can run on battery backup.

[urbanfarmer]

As long as the pump keeps running, you don't need bubbles. If the pump stops the bubbles buy you lots of time to fix it. Making bubbles costs very little in power or material and can run on battery backup.

With a high enough stocking density, this is most certainly true. Often, I find myself taking an exaggerated stance on something to prove a point. The Truth lies somewhere in between...