Duckweed and nitrate, ammonia removal

Spyro

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So, I came across this interesting study on food recycling. As we all know, what is one to do if one is respectable rich capitalist farmer with more money than one knows what to do with but sponsor a study to see if there is a way to recycle sh&t into food again and save few bucks on feed.
They experimented with duckweed being fast grower, etc. and came to some findings that might be interesting to some of you fish keepers. It certainly was interesting for me; but I get interested into random stuff easily, so there is that.

I'll do some theoretical examples of duckweed in tanks.

Scenario 1
-High tank with good filtration, substrate, decorations, etc.
Filtration, substrate, decorations offer lots of surface area and bacteria will have that ammonia turn into Nitrate for Duckweed to munch on.
Duckweed being fast grower will do good job munching on Nitrates and depending on stocking levels help with keeping those nitrates down but not remove them completely.

Scenario 2
- Shallow/long/wide tank. Bare bottom, no decorations, no filters, just fish.
Nightmare scenario for ammonia spikes and nitrogen cycle. There isn't much surface area for bacteria to colonize and thus no way to deal with that ammonia.
Here is a kicker:
Duckweed is 11 times more proficient in removing ammonia than nitrates. And being floating plant = more surface area means more ammonia removing power.
So theoretically: person in scenario 2 could conceivably have same fish stocking as person in scenario 2; While person in scenario 1 still has rising nitrates level with all that bacteria, filtration and duckweed. Person in scenario 2 has 0 ammonia or nitrates with just duckweed and fish in the tank.

Scenario 3
Person has same set up as person in scenario 2 but instead of tap water with 0 Nitrates, tap water with high nitrates.
Their fish keeps dying because of build up of ammonia and thus fish poisoning.
How? Well it turns out that high level of Nitrates in water also diminishes duckweed ability to use 11 times more ammonia then nitrates to about the same as nitrate;

And then depending on light, CO2, temp, etc duckweed ability to draw nitrates is lower than optimal conditions; thus someone with duckweed munching on ammonia might have much greater rate of removal than 11 times than someone with sub-optimal duckweed conditions.

No wonder people on fish forums keep arguing when differences between 2 seemingly identical setups can have such wast difference in end result.

Interesting? Thoughts anyone?

P.S. and if anyone has interest if capitalist managed to save few bucks by turning sh&t into food again: Well, it turns out it's not economical but they are still trying to make it economical so that duckweed can eat pig sh&t and then be feed back to pigs.
 

itiwhetu

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This whole subject fascinates me. From what I have done over the last 20 years almost. All you need to control Ammonia is lots of plants and an acid tank. I am surprised at how many Aquarists keep their fish in Alkaline systems, and then are surprised when they have problems. Also it is almost beyond belief that people would consider keeping fish without live plants as part of their ecosystem. I understand when it is Cichlids or some of the other large species of fish, but in a normal community tank live plants are a must. I also really struggle with Aquarists that clean gravel to get rid of fish poo, then add ferts into their tanks, for me this is completely counter productive. Leave the fish poo in the tank and don't add ferts. The fish poo will supply all the nutrients the plants need.
 
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Spyro

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This whole subject fascinates me. From what I have done over the last 20 years almost. All you need to control Ammonia is lots of plants and an acid tank. I am surprised at how many Aquarists keep their fish in Alkaline systems, and then are surprised when they have problems. Also it is almost beyond belief that people would consider keeping fish without live plants as part of their ecosystem. I understand when it is Cichlids or some of the other large species of fish, but in a normal community tank live plants are a must. I also really struggle with Aquarists that clean gravel to get rid of fish poo, then add ferts into their tanks, for me this is completely counter productive. Leave the fish poo in the tank and don't add ferts. The fish poo will supply all the nutrients the plants need.
Yeah, makes sense.
In defense of aquarists (especially newish ones): there is so much contradicting info everywhere, it's hard to weed through it when starting. Also seems to be a lot of engraved folklore myths from past and present lol
 

itiwhetu

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Yeah, makes sense.
In defense of aquarists (especially newish ones): there is so much contradicting info everywhere, it's hard to weed through it when starting. Also seems to be a lot of engraved folklore myths from past and present lol
The fundamentals of fish keeping is that plants need fish and fish need plants. If you start with that philosophy the rest is easy. A message to aquarists afraid of plants, Remember aquatic plants are weeds, so start with stemmed plants that are fast growing and once you have them established then move towards the other plant species.
 

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