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New to hydro, nutrient issues i think

12 years ago

Hello everyone,

New to this forum and hydroponics.

here's my situation.

I'm trying to grow a type of lettuce called "lolla rossa" as my first hydroponic crop.

This is my "second" attempt before trying to get some answers on this forum.

I'm using a raft system.

Basically i have a 9 liter container 30x35 cm, an air pump with air curtain attached. The air pump is designed for up to 57L containers.

For nutrients I am a bit limited as hydroponics is a non existing market where i live in Romania.

My plan is to use commercial nutrients for soil plants, and mix them and dose them in such a way that I can get acceptable nutrients in the end.

I am using a combination of these 2 nutrients:

nutrient A


nutrient B

As I can tell they contain a number of macro and micro elements, but they lack other elements like Ca, Mg and S.

I am using

2.11 the indicated dosage of A


0.58 the indicated dosage of B

This gives me in the end, at least on paper an NPK of 18-7-21 [actual elements not K20 or N03)

Here's my process:

Germination - I started the seeds [they are standard seeds, if that means anything to anyone] in a germination box, like a tupperware container. The seeds are placed in small cups filled with LECA, cooconut yarn, and very diluted soil plant nutrient.

The germination results were excellent IMO, i got 25/27 seeds to germinate in less than 1 week they had already cotyledons.

After 1 week I put the seedlings in half strength nutrient solution, explained above. They had started to grow quite nicely, They had their first true leaf. At this time i did not have a pH meter or EC meter. I used tap water to make the solution. I tested the tap water afterward it showed 0.3mS EC and 7.2pH. So i can say i was quite happy that the seedlings had grown in such high pH water. I also moved the container with the seedlings under a south facing window, they had been on the north side of the house until now since I was colder there during germination, and I figured if they had more sun they would grow better.

1 Week later I transplanted the seedlings to the 9L container, the actual hydroponic system. By this time I had a pH meter and EC meter.

I made the nutrient solution with half tap water [7.2] and half demineralized water [ph 6] and the nutrient formulation from above.

I reduced the pH of the water to 5.9 using 9 deg vinegar, about 13ml for the 9Liters. The EC of the solution was 1.2mS. The ambient temperature was around 20-25 degrees.

After the transplant to the raft system, i placed the system under the south facing window, and, in 3-4 days the plants started to show signs of weakness i would call it.

The stem of the leaves has a red/purple tint to it. Some leaves have tipburn. They also seem to have stopped growing, none of them have more than 2 true leaves, and those are kind of as big as the cotyledons [1cm wide by 2-3cm long]

The nutrient water also smells funny.

Can anyone point me in the right direction as to what I did wrong and how could I address the following issues, that I think are the problem with what I did.

I have these hypotheses, please feel free to shot them down, I'm new at this, and I'm still guessing in the dark.

1. The nutrient solution was not balanced. I mean it lacks Calcium and Magnesium. I calculated I'm missing about 120ppm Ca and 44ppm Mg for the 18-7-21 formula. Any ideas how to add these 2 elements? Epsom salts and some Calcium carbonate? Could it be unbalanced somehow because it is not "hydroponic nutrient". Is there any way I can get this to work using soil plant nutrients [not organic] and some other additives?

2. I transplanted the seedlings too soon. in retrospect, perhaps I should have waited 1 more week to do it?

3. The air pump is somehow pumping too much air into the system, perhaps encouraging microorganism growth in the nutrient?

Thanks for reading and feedback

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