Hydroponic fertiliser A and B for growth and flowering

Hydro A and B suits all inert grow media, clay pebbles, rockwool or perlite, as well as systems with no grow medium. It works equally well as run-to-waste or recirculating, which covers vertical towers, NFT channels, flood-and-drain tables and RDWC systems, where several pots share a single oxygenated sump tank. With run-to-waste, each watering receives fresh solution; with recirculation, the same sump tank circulates for several days, which is why it matters to replace it after four days.

In a coupled aquaponic system, the fish water circulates in a loop between the pond, the filter and the plants. Hydro A and B is a mineral fertiliser formulated for water without fish, so you should never add it to this circuit. The water of a well-run pond already supplies the plants with the nitrogen from the fish waste, in the form of nitrates, and most of the other elements.

Deficiencies in a coupled system mostly concern iron, potassium and calcium, because fish feed contains little of them. They are corrected with products that are safe for livestock: a DTPA chelated iron at around 2 mg/L roughly every three weeks, potassium bicarbonate or calcium carbonate, which raise both the pH and the carbonate hardness. These additions should be decided after a water test, not by the calendar.

In a decoupled aquaponic system, water from the pond feeds a recirculating plant loop that never returns to the fish. This loop works like a hydroponic system, and Hydro A and B has its place there: its potassium-rich bottle B and its calcium-rich bottle A supply exactly what the fish water provides least. You start from the pond water and add a fraction of the dose, in equal parts, until you reach the target conductivity. The article on the difference between aquaponics and hydroponics explains why the two systems are not fed in the same way.

The 100% HYDRO growing schedule increases the dose each week rather than fixing it from the outset. In the first week, you add 14 ml of Hydro A and 14 ml of Hydro B per 10 litres, then 16, 18, 20 and 22 ml, before reaching 25 ml of each from the sixth week, which is the maximum dose of 2.5 ml per litre. The conductivity follows the same movement, from 1.4 to 2.3 mS/cm, tap water included, and never exceeds 3.0. For lettuces or herbs that stay in leaf, you repeat the second-week dose for as long as the crop lasts. The schedule combines Hydro Roots at 10 ml per 10 litres for the first five weeks, and Green Sensation from the sixth week on fruiting vegetables. Euro Pebbles clay pebbles serve as the growing medium in this programme, rinsed before being put in place. If you start from osmosed water or rainwater, CalMag Pro first restores its calcium and magnesium, at 0.75 ml per litre, before Hydro A.