What should be the density of solutions


hey there,

I’d like to know what should be the densities of the pH/EC and A/B solutions in a hydroponic system? I believe pH shouldn’t be mixed up with water to decrease the concentration which would cause a lower original solution rate. But, since the A/B nutritions are too dense, wouldn’t it be a wise choice to add water to the cups to lower their density?

thanks in advance!

I don’t really understand what you are asking. Your “nutrient densities” should be what the manufacturer of the nutrients suggest on the bottle… they tell you what the mL per liter (or teaspoons per gallon) mixture ratio should be depending on your watering schedule… higher ratio for fewer waterings per day… lower ratio for more waterings per day. Always follow the nutrient manufacturer’s suggested mix ratios. As far as PPM or TDS measurements, ideally your nutrient solution should be between 800 and 1500. My personal experience is that less is actually better in hydroponics… never try to push your nutrient mix ratios higher than the manufactrer’s suggestions or you can end up with nutrient toxicity in your plants. Better to use the low or mid range mix ratio suggested by the manufacturer and run more frequent watering cycles (every 2-4 hours during lights on periods). As far as pH, you should always balance the pH of your water before you add any nutrients… and then re-balance the pH after all your nutrients are added to the water.
There are also other factors to consider… how many plants are you growing? What type of system are you using… flood & drain, ebb & flow, deep water culture, thin film technique? Different types of systems create different types of interactions between the roots and the nutrient solution. The more continual direct contact your roots have with your nutrient solution, the more your nutrient solution’s TDS and pH will change over time.
Personally, I have never needed to automate any nutrient checking or mixing. I know from years of experience that my nutrient solution can go for up to 5 weeks without needing to be changed, and the pH stays stable if I don’t use any organic nutrients or other organic products in the tank. My pH also stays pretty stable over 4-5 week periods, partially because I avoid organics in the tank, and also because I’m using flood & drain, so there is no continual contact between the nutrient solution and the roots like you would have in a DWC or ebb & flow system.

I try to follow Kyle’s blog, so you can consider there would be a pretty much the same environment as he did. But I couldn’t find the information in his blog about the density of the acid/base and A/B solutions that he uses in his cups (which he mixes via peristaltic pumps in the tank).

I agree with this.

I was kind of aware of this but since I didn’t have any experience in such type of system, I wasn’t sure what the densities in the solution bottles in the system were. It is kind of straightforward for pH solutions that they should stay pure in the bottles but couldn’t be sure about the nutrients since they are too dense and I was afraid to go higher concentration accidentally in my tank due to any misconfiguration in Mycodo that I would make.

I hope it is a bit clear right now :slight_smile:

So what are you planning on growing? How many plants? How large is your nutrient tank? Are you using the Nutrient Film Technique like in Kyle’s hydroponics build where you have water running through troughs that the plants sit in? That type of system is perfect for small, short types of plants, but it is not good for larger, taller types of plants where the roots need to hold up the plant. Also, that type of system requires that you have a watering pump running constantly, 24/7, or your plants will die because the roots are totally exposed (not in a grow medium that holds water). Also, realize that Kyle’s video is mostly showing proof of concept of what you can do with Mycodo… there are a few things in that build that would cause long term problems… mainly that you will end up with algae growing inside the troughs because they allow light to reach the roots and the nutrient solution flowing through them… which means you have to pull all the plants out and take the troughs out and be able to thoroughly clean them at least once a month to prevent algae from building up around your roots. Best rule of thumb for hydroponics is to never let light reach any of the water or nutrient solution in your system… anywhere you have light reaching your water, you will always end up with algae… and you don’t want algae in your system because it uses up nutrients as well as oxygen in your nutrient solution. The more you can do to prevent algae, the more stable your pH and nutrient levels will be over time.

The system Kyle built in that video is a really awesome setup, and he built it to show the full potential of what Mycodo is capable of doing… but in practical terms, and especially if this is your first hydroponics system… I would wait to automate the nutrient mixing and pH control until after you have the rest of your system running and dialed-in (lights, temperature, humidity, and watering). Automated or not, you will still need to drain and clean your nutrient tank (and the rest of the system) at least once per month to remove any algae, bio-films, and sediment that will build up. All those pumps, hoses, wires, sensors, cups, and such will make removing and cleaning the tank more difficult (unless you design it really well). I think automating the nutrient mixing is a bit overkill for a small system… if I were setting up a large hydroponics greenhouse, I’d definitely automate the nutrient mixing and pH control, but for a small system, like a grow tent, it’s not really necessary. I’ve been growing veggies in hydroponics on and off for almost 10 years, and I’ve been growing cannabis in hydroponics for the past 5 years. I mix my nutrients by hand once a month and then I don’t have to worry about it for another month other than topping off the tank with fresh water when needed (about once a week). I learned that my nutrient tank stayed pretty stable for up to 5 weeks as far as TDS and pH measurements as long as the water temps were kept below 77 F and I did not use organic additives (anything that can rot or decompose and cause bacterial blooms)… also aerating your tank with a good aquarium air pump and air stones is absolutely essential for preventing bad bacterial blooms and keeping pH stable. As far as the type of system goes I think flood & drain is the simplest type of system to build as well as clean and maintain. Flood and drain is also more tolerant of failures… because your plants are growing in pots with a grow medium like coco coir or hydroton clay pellets that can hold water for a day or so… so if your watering pump fails, your plants will still survive for a day or 2. Also, because your plants are in pots, it’s really easy to remove them from the flood table for pruning, and also so you can easily clean the flood table.


I am planning to grow lettuce and basil as a beginning. On average, there would be more than 50~60 plants in the system. Even though NFT is an impressive technique, I decided to try a vertical planting setup as it gained some popularity in the last few years. It also helps to save more area according to my research.

It is not possible to prevent light into the water in my design but I wonder whether you would encourage using solutions to prevent algae and fungi for instance.

Trying as much as I can for this :slight_smile: I mean that is the final goal but again, mixing some bio-based solutions for preventing these kinds of situations should be available on the market, right?

Thanks for sharing your experience though. You wouldn’t know how valuable these are for me. I’d like to ask that do you keep your aquarium air pump and stone on 7/24? Thanks in advance!

I have actually built and used a couple of vertical systems for short crops like lettuce and other salad greens and cooking herbs. I really liked them because they worked great and saved a lot of floor space, but they did have some problems with algae buildup over time. There is simply no way to totally prevent algae, it’s just one of those things you have to learn to deal with when growing in hydroponics… which is why it’s good to design your system so that the least amount of light possible reaches your nutrient solution, and everything can be easily taken apart and cleaned on a very regular basis. There are biocides and algaecides available for controlling algae, but the problem with those is that they are expensive, and they don’t just attack the algae, they also stunt the growth of other plants, so you want to avoid using chemical algaecides if possible. There is also the question of if those chemicals are safe to be using on a food crop that you will be eating. For spot-treating algae that grows in hard to reach places, spraying a little 3% hydrogen peroxide on algae spots usually kills them, but you also have to be careful not to get it on your plant’s leaves or roots because it can burn them unless it’s diluted. And peroxide is safe to use on food crops. As far as the air pump, it needs to run 24/7… I even run an air stone in my 5 gallon humidifier tank.

I’ll try my best on this.

Totally agree.

In general, thank you for the advice. It was nice to have such a conversation with you. Learned a lot!