Hydroponic reservoir maintenance: a weekly routine for hydro and DWC

Reservoir maintenance at a glance

In hydro and DWC the reservoir is the root zone: the nutrient solution is how the plant receives its mineral elements, so its condition affects every plant in the system. The table separates Monkey Nutrients feeding information from general hydroponics practice, so you can see which is which.

Change the reservoir weekly

Change the nutrient solution in the reservoir weekly. Through the week, plants take up water and nutrients at different rates, so the solution in the tank gradually drifts away from what you mixed. A full change resets it to a known, freshly mixed solution and gives you a regular moment to inspect the tank and the roots.

General guidance: between changes, many growers top up the reservoir as the level falls. Topping up keeps the roots supplied, but it does not reset the balance of the solution, so treat it as a stopgap rather than a replacement for the weekly full change. Note what you added and when, and check EC and pH after topping up.

Mixing a fresh tank: EC and pH

Measure the water volume first, then use the Feed Chart or Feed Calculator for the week you are on; the calculator scales the per-10-litre chart amounts to your reservoir and shows the mixing order to follow. The Monkey EC guidance is the same across media, so a hydro reservoir uses the same EC targets as coco and soil.

The Monkey chart pH range is 5.5–6.5. As general guidance only, not a label claim, hydro and DWC typically sit at about 5.5–6.2, coco at about 5.5–6.2 and soil a little higher at about 6.0–6.5. Check pH after mixing and before feeding; the EC and pH guide explains how to measure and adjust.

Water temperature and oxygen (general guidance)

This section is general hydroponics practice, not Monkey Nutrients label or chart information. Cooler water holds more dissolved oxygen than warm water, and warm, poorly oxygenated or stagnant solution is commonly linked with root problems such as root rot. Keep the reservoir away from direct heat, check the solution temperature with a thermometer and keep air pumps and air stones running so the solution keeps moving.

We do not give a target temperature here. Monitor your own system over time and treat any change in root colour, smell or texture as a reason to look closer. The root rot guide describes the signs to watch for.

Cleaning the tank and equipment (general guidance)

A clean reservoir gives you a clearer picture of what the roots are experiencing. As general good practice, empty the tank at each full change, wipe away residue and any slime, and rinse thoroughly before refilling. Between runs, clean the tank, pipes, pumps, air lines and air stones, and keep tools used on one system away from another until they are cleaned.

Light reaching the solution encourages algae, so use an opaque tank and keep the lid closed. If you use a cleaning product, follow its own instructions and rinse thoroughly before the fresh mix goes in.

Cal-Mag in a hydro reservoir

Monkey Mag Cal is used at 1–2 ml per litre. Feeding is the same in DWC and hydro, so a DWC reservoir follows the same Mag Cal guidance as other hydro systems. Do not add Mag Cal in the flush week.

Base feeding comes from Grow A+B in veg and Bloom A+B in flower; both are designed for coco, soil and hydroponic systems.

Ultra Zyme and the root zone

Ultra Zyme is an enzyme plant supplement and appears in the Monkey feed chart alongside the base feeds. It is part of the feeding programme, not a substitute for weekly changes, a clean tank and a well-oxygenated solution. No Monkey Nutrients product is presented as preventing, treating or curing root problems.

Flushing and storing nutrients

At the end of flower, flush for at least 1 week. Mag Cal is not added in the flush week. Keep checking pH against the chart range while you flush.

Store your nutrients according to the storage notes and the date on each bottle. We do not give a separate shelf-life figure: the bottle is the reference.

Weekly reservoir checklist

Work through the same routine at every change and keep a simple log. If plants start to look wrong, check pH, EC and roots before changing the feed; the nutrient deficiency guide explains why lockout and root problems can look like a shortage.

1. Empty the reservoir and inspect the roots for colour, smell and texture.
2. Clean the tank and rinse it thoroughly (general guidance).
3. Refill with a measured volume of water and mix the week’s amounts from the Feed Chart or Feed Calculator.
4. Add Mag Cal at 1–2 ml per litre where your feed plan includes it, but not in the flush week.
5. Check EC and pH after mixing and before feeding; keep pH within 5.5–6.5.
6. Check aeration and solution temperature, and note the date of the change (general guidance).