"Reading" Red Root Floaters

Nitrate levels matter.

Above: At sustained very low nitrate levels, they turn deep red.

Above: At high nitrate levels, they turn completely green.

The red floaters were grown at around 200 umols of PAR compared to the green floaters at 400+ umols of PAR. Stronger light can turn them redder, but the relative impact of nitrate levels is greater.

How to use them:

• If you wonder about the broad level of nitrates in your aquarium and don’t want to use a test kit, red root floaters is a fun way to get an indication. Remember: the clue is in the colour of the NEW leaves that develop in the tank.
• If your red root floaters are very green and if you are struggling with algae problems, especially Green Dust Algae, lowering nitrates is one factor that often helps. Use APT 1 which has no nitrates, or reduce dosage of APT 3.
• If your red root floaters have been extremely red for a long time, this may be an indication of too lean conditions. Plants may look healthy but can be very brittle. This is common in very mature tanks where lean dosing is used.

How to read the signals

• Observe only the newest leaves. Like ’tree rings’, the older leaves record the past, the newest leaves the most recent environment.
• Other things being constant, if the new leaves are turning redder, your nitrate levels are dropping.
• Other things being constant, If the new leaves are turning greener, your nitrate levels are rising.

Target colour?

In most 2Hr tanks, the residual nitrate (NO3) level in the water at the end of a normal week before a water change is usually below 5ppm (often close to zero). This is the residual level after plant uptake and at this level plants are healthy and algae is easy to control.

At <5ppm, red root floaters are greenish-yellow-red as shown below. However they are more useful as directional indicators, and not to gauge the absolute amount of nitrates present.