Backyard Aquaponics
A place to discuss aquaponics

Hello all, I'm completely to aquaponics and in need of advice. I've posted a pic of an outdoor pond my dad has in his backyard on that i wish to convert into an aquaponics system. The following is the progress I've made along with a few inquiries I have.


The pond houses comet goldfish and my dad has a pump that pumps water from the pond into a recycle bin filled with gravel to filter the water (pics attached)

So the first thing I did was to test the water levels of the nitrites, nitrates and ph in the water directly above the gravel. I don't know if this was the correct thing to do since I'm assuming there might be nitrifying bacteria present inside the actual gravel that does not begin converting the ammonia in the system until it filters through the gravel. Both nitrite and nitrate levels where at zero, the ph was neutral at 7. My first question, should I scoop out a bit of the gravel, strain the water in it, and test that for nitrates instead?

I also tested the ammonia of the water in the actual pond, which seemed very high to me, at 2ppm (pic attached). I have no experience in determining what an adequate ammonia level is, but these fish have lived there for years, none of them die, and the seem to be thriving, so although the ammonia level seem high to me, I'm assuming it is within some tolerable level since the fish aren't dyeing. I'm aware that ionized ammonium is much less toxic to the fish than NH3 is (or vice versa?), so I'm assuming that the less toxic ammonia is present in the majority

How would you guys proceed from here?

You should be getting nitrates - maybe the plants in the pond are using them all? Try testing the water coming out of the gravel drum. That's the most likely place to find the bacteria doing their work. I'm thinking the nitrates head back to the pond where the plants have nice nutrients to gobble.

So if you are going for a veggie- producing AP system you will have to remove those plants - they will compete with your veggies for the nutrients.

Another thought - I wonder how much DO you have in the gravel drum? It may be an anaerobic environment through most of it.

Yeah that's what I figured, I'm going to test the nitrates coming out of the gravel pit before its recirculated into the pond, just wanted to confirm here first.

As per DO, this is short for dissolved oxygen? If so what is the significance of the level of do in a system?

I have some background in chemistry, and I remember doing a titration using sodium thiosulfate to determine the dissolved oxygen in a water sample, is this th easiest method of testing for it?

Yes DO is dissolved oxygen - significance is things die without it. Plants AND fish need it. I've found I can turn my pump off for up to 12 hours (for heat retention on cold nights) and everything is fine because I have plenty of DO from airstones.

Not sure about the measuring but if you have a method like that one, maybe tell us what you do please?

Well, a titration consists of a sample with an unknown content of whatever it is you're testing for, and a solution of a known concentration you will titration it with.

For example, lets say you have vinegar (acetic acid) and lye (potassium hydroxide), you want to know the concentration of the lye, and you already know the concentration of the vinegar. So you pour your acid, the vinegar, into your base, the lye, and eventually the acid will neutralize the base. A few drops of ph indicator will cause the solution to change color when the neutralization occurs. If you measure how much vinegar was used to achieve the color change, you can then determine the concentration of the lye.

The same concept applies when using sodium thiosulfate to titrate water to determine the DO concentration,

This link gives the relevant equations necessary

http://water.me.vccs.edu/concepts/domeasure.html

Interesting..

Here's a detailed explanation on how to measure DO, using this method, which is called the winkler titration. Its a bit involved but should give a very accurate result for your trouble.

http://youtu.be/FKdzbgHaQQM

Update:

So I tested the water coming out of the gravel put and it still has ammonia reading at about 2ppm, I've also dug out some of the gravel from the middle of the gravel pit, and tested that water, I have absolutely no idea why there are still no nitrite/ates. This pond has been therefor years so I'm assuming that nitryfying bacteria has more than enough time to have formed, any suggestions?