Nutrient Uptake - Changing Water Every Two Weeks and Testing

by Eric Bacca
(Huntington Beach, CA. USA)

I would like to know about your suggestion for using two reservoirs- one for nutrients one for the water. Would this system be a recovery system? and wouldn't I need a third reservoir for the used hydroponic nutrient solution, since the other two are separated?

Do you use a fertilizer injection system? I have been reading that a lot of commercial or large hobbyist do not ever empty the reservoir....only replenish low levels and correct nutrient imbalances. I have a TDS /EC meter which I use. How do you tell what specific nutrients are being most used each day or over a period of time?

Also, do you ever have a problem with Salmonella, and how do you take your preventative measures to reduce the risk? Have you ever tried ozone water injection to prevent algae growth and sterilize harvested crops? And have you ever used CO2 water injection to lower pH (if needed) and supply CO2 to the water oppose to the air? Thanks for the helpful and informative site and for your time. Best Regards, Eric.

Answer: Eric- the point of having a "two reservoir" system is simply that you will have a whole reservoir full of de-chlorinated, room temperature water conveniently waiting for you to "swap out" with the old nutrients next time you go to do a nutrient change. In my particular hydroponic system, I re-circulate the nutrient solution through the system. The nutrient reservoir acts as both the nutrient reservoir AND the recovery tank for the system, therefore I only needed two reservoirs in my example.

Unless you are running ten 1000 watt lights or more, it would not be cost effective to use the same techniques as a person trying to manage an enormous garden. Specifically, the cost of a nutrient injection system to manage your nutrient solution and the cost of sophisticated water tests (way more info than what you get from your TDS meter) that detail the levels of every individual nutrient would both be a waste of money for a small gardener.

Instead, the vast majority of all indoor gardeners use a very different strategy to keep the nutrient solution right. Nutrients are mixed at full strength, and the garden is allowed to feed off of those nutrients for about two weeks. If the water level gets low, the reservoir is topped off in between changes with 50% strength nutrient solution.

After two weeks, the chances are pretty good the plants have fed upon certain nutrients more than others- to the point of causing a nutrient imbalance in the solution. Dump the whole reservoir and start over with fresh water and nutrients. For more detailed information on maintaining the nutrient solution properly, check out the how to grow hydro page.

Personally I have never had a problem with Salmonella, have never used ozone injection, and have never used CO2 injection in the water. I believe the best combat against algae is simply designing your system to prevent any of the nutrient solution from coming in contact with any of the light. I have never had the need to "sterilize" any of my crops, but I do sterilize my hydroponic system in between crops with a 5% bleach solution (and tap water). Wiping down your garden area should also help prevent Salmonella. Hope this helps, and Happy Growing!

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(10 week update below)

Find out the cheapest and easiest ways to garden productively in this article.

Hi everyone, Jason from Jason's Indoor Guide here. When I got started with hydroponic gardening more than 24 years ago, my first garden used rockwool cubes and B.C. Nutrients....and I remember thinking to myself yeah, sure, there may be a lot of advantages to gardening with hydroponics, for example there are very few pest problems, therefore very little pest control, no weeding, no plowing or tilling the soil, no soil testing or having to add things into the garden soil, no watering the garden....but for someone who just wants to grow their own vegetables and have more control over their food supply and the quality of the food that they eat, the cost of constantly having to buy grow media and hydroponic nutrients makes this an expensive hobby for most people...

Epic Nutrient Change

I suppose when you take into consideration how much money you save NOT having to buy food at the grocery store, it is surely cheaper to grow your own food hydroponically even with the cost of high quality nutrients. Nevertheless, I didn't have a whole lot of money to work with and I needed to make my efforts as affordable and effective as possible....and in the last 24 years I HAVE learned a thing or two!

As you browse through Jason's Indoor Guide, you will notice all of the systems that I use personally are homemade systems. As I got 3 or 4 years of experience under my belt, I quickly adopted a preference to standing water systems and systems that use expanded clay pellets or lava rock, because the media is re-usable and it eliminates a huge operating expense. So once a hydroponic system is built, garden maintenance is minimal- check and adjust the nutrient solution daily, and to change it completely every 2 weeks....and the biggest operating cost is the hydroponic nutrients. (and the electric bill, lol)...

Homemade Cloner

And, regarding the cost of the nutrients....I experimented for about 3 years with making different compost teas and nutrient teas, but there is still a lot of expense $$$ associated with making high quality nutrient kelp meal, liquid seaweed, rock dust, bat guano, un-Sulfured molasses, worm castings. You can eliminate a lot of this expense by becoming an expert at making high-quality colloidal humus compost, and use your properly made compost as the basis of your hydroponic nutrient solution.

Unfortunately, I have been gardening for over 24 years and I have only just recently mastered this difficult skill....and even then, only because I happened to find a very easy to follow, high quality technique and decided to follow the instructions to the letter. I produced more high quality compost in just one week than I was able to use in a whole year! If you can master the technique, I highly recommend it. It is one of the top 3 things you can do to increase the productivity of your food production efforts, while at the same time decreasing the amount of effort required to grow all of your own food, and decreasing the total cost of operating your food production system.

And when I say decrease operating costs, I mean decrease them to almost ZERO, especially if you are producing your own nutrients...

High Efficiency

The ultimate solution to eliminate the cost of your hydroponic nutrients: Imagine a hydroponic system that does not require you to buy any nutrients, does not require you to make your own compost, and does not require you to brew your own nutrient tea. Seriously! No cost and no effort as far as providing nutrients to your plants! Plus, at the end of the gardening cycle you harvest all of your garden vegetables, PLUS YOU HARVEST FISH from the system--->


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This solution is aquaponics. If you are serious about producing all of your own food and being self-sufficient, this is the ultimate solution for reducing expenses (as much as possible), reducing the total amount of work required, and maximizing the productivity of your gardening efforts. I have been gardening for over 24 years, and it is the perfect food production solution in my opinion.

Produce garnden vegetables AND fish together. Eliminate fertilizer costs!

Besides mastering how to make high quality compost, learning aquaponics is one of the top 3 things you can do to increase your garden productivity, reduce your total costs, and reduce your total work. The product that I learned from is called Aquaponics4you. With all of my hydroponic gardening experience, the first time I came across the Aquaponics4you product I knew immediately that it was something very special! Place an aquaponics system outdoors and use the sun instead of grow lights, and you have reduced every garden expense to nearly ZERO!

The Same System/ 10 Weeks Later!

If you've found this site helpful at all, I would really appreciate it