Hydroponic pack for 20 plants: system, grow medium and nutrients

Doses are given per litre of solution, to be multiplied by the volume you are preparing. In full growth and in hydroponics, allow 1.8 ml of Grow, 1.2 ml of Micro and 0.6 ml of Bloom per litre. In flowering, the ratio is reversed, with Bloom rising to 2.4 ml and Micro to 1.6 ml. Aim for a conductivity of 1.3 to 1.8 mS in full growth, and a pH of 5.5 to 6.5. Adjust the pH last, once all three parts have been added, because each one changes the value. In 150 litres, a correction takes around forty minutes to spread through the solution despite the constant circulation, and the check reading should be taken after that delay rather than straight after pouring. Our article on pH regulation covers measuring and correcting in detail.

The test supplied is colorimetric: a few drops of reagent in a sample, then you compare the colour against the chart. The 60 ml bottle comfortably covers a season of frequent measurements, and it needs no calibration, no buffer solution and no battery. Two conditions are needed for the reading to be worth anything: daylight and a white background, because pink horticultural lighting makes the comparison impossible. In practice you read to the half point, not the tenth, which is more than enough to hold a range. Always sample from the same spot in the reservoir and after mixing, as a sample taken just after an addition does not represent the whole reservoir. Store the bottle away from light, as colorimetric reagents lose accuracy once exposed to sunlight for long periods.

The pH-lowering product supplied is 100% urea phosphate, a powder that is inert when dry and turns acidic once dissolved. Dissolve it at 1 g per 5 to 6 litres of water, then add this correction solution in small amounts, measuring after each addition, as the total quantity depends on the hardness of your water. This salt is made of urea and phosphoric acid, so it adds phosphorus and nitrogen to the solution as well as lowering the pH. At a typical correction dose the contribution is marginal, but it explains why very hard water that needs a lot of pH down ends up more heavily loaded than expected. The 250 g supplied cover several complete refills of the tank with water of average hardness. Store the powder dry and sealed, as it absorbs moisture from the air and eventually cakes into a block that is difficult to dose.

Assemble the system dry following the instructions, then fill with clean water and run it for an hour: you are checking for leaks and, above all, that the flow is equal across the four channels. Rinse the clay pebbles, fill the baskets, prepare the solution, adjust the pH, and transplant plants that are already rooted. After that, the solution is replaced entirely every 2 to 3 weeks; between replacements, you only make up for evaporation with clean water. If your plants are not ready, our article on the indoor seedling area describes the corner to set up 3 to 4 weeks beforehand. During the first week, a daily check of the level, the pH and the look of the roots will reveal an installation fault much earlier than a weekly check.

The 4 linear metres of gutter are best given over to short, low-growing crops: lettuce, mesclun, spinach, basil, parsley, chives, mint and strawberries. Tomatoes and peppers grow there too, at a rate of one space in two, since a single plant develops as much foliage as 2 to 3 lettuces and is staked on a structure independent of the system. To keep all 20 places filled, stagger your plantings: each harvest frees up a basket, which immediately receives a young plant prepared in advance. Our guide what to plant in hydroponics gives the cycles species by species.

Between crops, scrub the four gutters with clean water and the brush supplied, without detergent, as detergents leave a film on the plastic, then rinse thoroughly. Each time you renew the solution, rinse the pump strainer and compare the flow from the four gutters, since a gutter that is getting less points to a deposit in its distribution fitting. The drain kit supplied saves you from bailing out 150 litres by hand: connect it as soon as you assemble the system, at an accessible spot. Also note the reservoir level each week, since a sudden drop with no change in the plants often betrays a leaking cap seal. In hard water, flushing with diluted white vinegar once a season, followed by two rinses, dissolves limescale before it reduces the flow.