Backyard Aquaponics
A place to discuss aquaponics

Another forum I frequent is at www.monsterfishkeepers.com. There's a guy there that wants to use plants in his aquarium sump for filtratino and I started talking him/them about the 'ponics. A fella named Miles posted this in response to the fella that wants to use plants in his sump as a filter...

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"Keep in mind,

While Plants help consume Ammonia, Nitrite, and Nitrate in different stages of the Nitrogen Cycle.. They DO NOT remove Dissolved Organics!

So, no matter how powerful the de-nitrator, nothing replaces the need for water changes.

(PS ~ Don't say Carbon removes dissolved organics, because then I will just say.. without water changes over a period of time your nitrifying bacteria will consume the minerals that make up your alkalinity and your pH will become unstable.)"

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So I respond:
Miles,

From my understanding water changes are not necessary if you have the right growing medium and plants in the system. Commercial aquaponics systems stock fish at densities of 1lb per 2 gallons of water (to 4 gallons of grow medium...1/2/4) In these systems water change is not done, you just top off the tank.

What sort of dissolved organics are you worried about? I'm not saying you're wrong, it's just the first I've heard of this. I've seen pictures/video of huge aquaponic systems (thousands of liters) and I don't believe any of them do water changes because that would take away plant nutrients. I'm going to run this by the aquaponics forum I vist and see what they have to say. I like things I don't know about

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And lastly, his response...

mrgrackle,

Commercial sized systems would probably be fine.. main reasons is they would use plants for nitrate breakdown, carbon for dissolved organics removal, and top-off for nutrient replenishment.. This is fine, for a commercial sized system. The top-off nutrient replacement, when losing hundreds of gallons of water each day from evaporation, is more than enough to constitute keeping the alkalinity up in the water..

In a small home-based domestic aquarium, not so much the case. 2-3 gallons of top-off water is simply not enough to replenish the needs of a well-stocked home aquarium.

The dissolved organics I am worried about, are dissolved organic compounds.. (DOCs) The waste product of fish that can not be broken down by the nitrogen cycle, and can only be removed through resins and water changes.

Also, the large hydroponics system you might be talking about doesn't necessarily 'change' water, not most commercial sized systems do.. They would have a 'flow-through' or 'drip' system to replenish nutrients and keep the water stable.. a bit differing from home aquaria. With a drip system, they would have to inject Co2 and Nitrates however..


My 1750g system at work never 'changes' water, but constantly has fresh water flowing into it.. and I stock about 6000-8000 units on that fish wall, no de-nitrator either. But Nitrates never get above 20ppm..

You might ask them.. If they only 'top off' and don't have a 'flow through system'.. then what controls Dissolved Organic Compounds? The Plants? Also, ask them how they keep their alkalinity up.. is it from simply topping off?..

One scenario I could see is that, if you rely solely on planted aquaria to keep your water quality pristine, you will have less nitrifying bacteria in the system.. and Nitrifying Bacteria is the primary consumer of the minerals that make up your alkalinity. So, if you rely on plants, your alkalinity should diminish less rapidly than if you relied on biological filtration.

I have heard of alot of 'self-sustaining' systems before.. It seems the larger the system, the more self-sustaining it can be.. I know that the large aquaria in Nevada's casinos does not do water changes, but only replaces lost evaporation water. However, their tanks are filled with sickly looking fish, very high nitrates, and the longevity of the fish in their care is shortened compared to large scale aquaria that performed water changes. Hole in the Head and Lateral Line Erosion is a very common disease in these large public aquariums that don't change water frequently.. lack of minerals.

Maybe some more information can be provided so we can continue this topic?

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So... what are these dissolved organics and how does the aquaponics system deal with these? I know people put shells, etc in their systems to get and buffer the pH up to 7.5.

Thought they used foam fractinators not resins to remove dissolved organics esp in marine systems.

mrgrackle, link him (and the other members) directly to the forum here....

Perhaps link directly to the forum page of member systems that display the growbed setups and plant growth.... http://backyardaquaponics.com/forum/viewforum.php?f=18

Or someone like Fayes system .... http://backyardaquaponics.com/forum/vie ... php?t=1622

Maybe even just link him to the BYAP front domain page ... http://backyardaquaponics.com .... for an overwview.

He seems to relate everything back to aquaria and aquarium keeping... I don't think he fully grasps the concept of EXTERNAL growbeds acting as solids removers and bio-filters....

maybe he isn't getting the fact many of us have systems in the range of 1000's of liters.
it's a known issue that your water's ph will slowly fall, but we have ways to balance that easily....

he kept mentioning hydroponics when you said aquaponics......................

and calcium carbonate will take care of the alkalinity in a non marine system

anyone who wants to argue with that feel free to explain to me how i have kept a stable ph of 7.4 for more than a year..............

regarding the foam factionators i think they are used more commonly in marine aquaria as they work much better with smaller bubble sizer that is obtainable in salt water compared to fresh water.

Someone mentioned there are "fresh water" fractionators on the market now.... not sure what the point of them really is though?

probably the same reason in marine aquaria, to my knowledge to remove protein before it is converted to ammonia ?

Yes, link them here. I don't do water changes, I moderate the pH with crushed shell and potassium bicarbonate, and the worms take care of solids.

I'm not quite sure what Miles means by DOCs -- are we sure that's not actually the micronutrients that the plants need in addition to the nitrate?

I was merely pointing out that foam fractinators are normally used to remove DOC's rather than resins which tend to be target specific and require repleneshing. I could possibly see an application in AP for Fractinators prior to return water to FT. Not only would you get the benefit of degassing but also removal of particles which would be likely to always stay in suspension possibly pulling down DO levels.
This of course is theroretical but I'm always up for an argument

I don't think anyone has found the need Sleepe, most people would attest to the water being returned to the tank basically clean and clear....

The return itself (if designed correctly) seems to provide sufficient oxygenation except perhaps at extreme temperatures.

The growbeds seem to trap most fine particles forming a layer of silty sludge at the bottom of the growbeds which a few worms will happily cleanup.

What about Doug's DFT system? And I suspect if you ran the return through a, say, .25micron filter you would be surprised at what you can't actually see.

My main concern is that DOC's could account for rapid oxygen depletion on power outs or system failures and account for some of the 'unexplained' fish deaths at this time.

Anyway just been writing to the pollies again and it always makes me stroppy

It is a possibility Sleepe.... just not sure, apart from using a .25 micron filter, how we'd go about quantifying it and the possible effects. You may be right re: oxygen depletion.

My indoor 650L aquarium has not had a filter change in 10 months.
The other day the O-Ring broke, and we were leaking water. So I switched it off to deal with later.
A high stress time made me say 'F*** it' they can all die, and resulted in 3 days the filter being off - 0 oxygenation - little ammonia uptake.
Turned it back on after 3 days, and all fishies are happy.
I would say - mature system = all good, and these tiny things may exists but didn't bother me.
Any Ideas?

Ok got over it; do the experiment first, post the results later.

I've been tearing the internet apart learning about dissolved organic matter (DOM) and this is what I've learned. Basically DOM is made up of any carbon compounds (contain at least a carbon and hydrogen atom) that are dissolved in water... dissolved meaning they will pass through a .25 micron- 1. micron screen. Anything caught in that screen would be particulate organic matter (POM).

Organic compounds in the ocean can change their state pretty quickly due to living organisms using them, then that organism dies/is used by another organism, producing other organic compounds, which are then used/converted by other organisms. Each time this happens the compounds become more refractory, meaning they become less and less usefull to organisms. The eventually end up in a state where there's nothing that uses them and thus are considered waste.

Can anyone confirm that I've got the basic concept down?

So it would seem to me that if the compounds are waste that nothing can use then they're pretty much non-reactive right? Also, in an aquaponics system we're constantly removing organic matter from the system in the form of fish and plants, so maybe this is where a lot of this stuff goes... the fish and plants aren't rotting in the system, going back into the water... imagine the mess of that!

In traditional aquariums you don't really take very much out of the system.. you just keep putting food into it. Plants that you do have are probably planted underwater and can't even respirate with the atmosphere (and perhaps remove organic compounds from the system).

Hmmmmm?