Need help with hydroponic questions

[Sylvia Bernstein]

I love talking with hydroponic gardeners about aquaponics.  They just can't believe that aquaponics works as well as we all know it does.  The reaction is typically "now let me get this straight...no EC meter?  No muli-part, expensive nutrients? And you never dump out the nutrients?"  It is fun.

There one question that occasionally comes up that I just got from a commercial grower in Spain through LinkedIn that I can't answer very well and I'm hoping someone in this community can help me out.  He asks "Do you have info you can share on the chemical composition of the fish waste? How do you adjust it to the plants' requirements? "

The second question can be handled with a simple...you don't have to, just like you wouldn't in a dirt environment, but you could do some slight tweeking of potassium, iron, phosphorus etc. if you really think you need to (I never have).

The first question, though, is knowable through lab tests...I just don't know of anyone who has done this.  Do you?

[TCLynx]

Well silvia, if the water is re-cycling constantly, you could probably scoop a sample from anywhere in the system and have tests done. It is still probably comparing apples to oranges a bit but it should still give some interesting numbers to chew on.

I would probably scoop the sample from the water coming out of the grow beds of a very mature and productive system for the test. Or if you have the budget, maybe sample water in a few different parts of the system to see if there is much difference.

Some useful tests could also probably be done on the fish feed itself since I do know that using poor quality fish feed will usually result in deficient plant growth.

[Sylvia Bernstein]

Thanks, TC. Good thoughts. No plant issues here - everything is growing beautifully - just trying to be prepared for a presentation I'm giving at Grow2010 in LA next week. Mostly hydro folks and I think this may come up.

TCLynx said:

Well silvia, if the water is re-cycling constantly, you could probably scoop a sample from anywhere in the system and have tests done. It is still probably comparing apples to oranges a bit but it should still give some interesting numbers to chew on.

I would probably scoop the sample from the water coming out of the grow beds of a very mature and productive system for the test. Or if you have the budget, maybe sample water in a few different parts of the system to see if there is much difference.

Some useful tests could also probably be done on the fish feed itself since I do know that using poor quality fish feed will usually result in deficient plant growth.

[TCLynx]

Sylvia Bernstein said:

Thanks, TC. Good thoughts. No plant issues here - everything is growing beautifully - just trying to be prepared for a presentation I'm giving at Grow2010 in LA next week. Mostly hydro folks and I think this may come up.

Yep, I understand. And once you manage to get some of this info, it will be a really useful tool not just for use with Hydro folks but for all sorts of things. Good luck in your search or getting the actual tests done as I suspect you will have to do.

[M Cosmo]

I ran my Vertigro as hydroponic before I went into the light. Tim at Vertigro recommended QAL labs to test the water from my well to understand what nutrients are in it already. I have attached the test submission form. I never did the test. But Tim said to mark it for Hydroponics. You might want to resource this lab or another Hydro water test lab to see if you need a different test. As i remember you have extensive experience in this so this post may be of little use to you. But others may benefit from what you recommend.

[Sylvia Bernstein]

Thanks, Kobus, but I'm already all over that study buddy - it's linked to on my website and I probably quoted it 20 times at the trade show ;-). I actually found the hydro people pretty open to it. They are all about finding better, more productive ways to grow. Now the nutrient manufacturers might have a whole different perspective...

Kobus Jooste said:

Sylvia - I just saw this thread now. Sorry I did not add to it earlier because I think it may have helped at the grow show. Please let me know if you are still looking for more info on this topic as I think I may have what you are looking for, but it is a bit all over the place. The hydro people may not like it as it clearly shows that AP works better than Hydro in straight comparative experiments. Better yet, the work was done by a Hydro expert at a University. The document is a bit bulky to attach, but if you search "Evaluation and Development of Aquaponics Production and Product Market Capabilities in Alberta. Phase II." by Nick Savidov you should get it. In it he has a section where he compared AP to Hydro, first by analysing AP solution and trying to make a hydro mix to run parallel tests, and then one where he made a standard Hydro solution to pit against AP. AP won both rounds. In the text you will find good info on the macro- and micro nutrients at play, but also the man's reasoning that it was the AP process, and not only the nutrient levels, that was key. My kind of man - he understands the ECOSYSTEM concept!!

If this is not enough, I have info on aquaculture sludge nutrients, but this is highly feed dependent. Citing Savidov has always been more rewarding to me.

[TCLynx]

This is rather cool.
I got into Hydroponics back around 2006 I think and much of the "online" thinking on the forums I joined then was probably just starting to shift a little away from the absolute need for complete sterility. Some people were still set on the need for sterilization but one of the forums I frequented has people who were using wood chip mulch as media and that is definitely not sterile and some were even using it for a second season with no sterilization between.

Anyway, I'm now hearing (very indirectly I must admit) that more and more hydroponic growers are attempting more "organic" methods than ever before. (Challenge is if you try to use organics and also use sterilization, you often wind up with nasty blooms of bad bacteria catching on before any good bacteria can really take hold enough to improve the system.) But little by little, more people are learning that it is possible to let go of a little control in order to allow and assist in balancing a healthy "non-sterile" ecosystem to develop based on the same principles that Aquaponics uses.

I'm really glad to hear from Sylvia that more and more hydroponics folks are catching on and becoming open to the ideas of aquaponics.