Spot-Treating Algae: Liquid Carbon, Hydrogen Peroxide and Manual Removal

How to target stubborn algae directly with spot-dosed liquid carbon or 3% hydrogen peroxide, why whole-tank dosing is a bad idea, and why manual removal comes first.

Why spot-treat instead of dosing the whole tank

The 2Hr Aquarist warns against pouring anti-algae agents into the whole tank: they are usually only effective at high concentrations, and at those levels they risk damaging the fragile microbial community that keeps a tank stable. Spot-dosing lets you hit the algae directly without exposing the whole system.

3% hydrogen peroxide

Ordinary 3% hydrogen peroxide (the drug-store strength) can be applied directly to affected plants and hardscape. As a plant dip the 2Hr Aquarist describes spraying it on, leaving it about 20 seconds, then rinsing it off. Apply it to the target with the filter briefly off so it is not immediately washed away.

Liquid carbon and algaecide gels

Targeted products such as APT Fix can be spot-dosed at up to about 1 ml per 10 L every 24 hours, applied directly onto slow growers like Bucephalandra, Anubias and Alternanthera reineckii, according to the 2Hr Aquarist. Stay within the label rate.

Manual removal comes first

The first line of defence is always mechanical. Tropica recommends wiping the glass with a soft sponge, cutting off badly affected leaves, and rinsing hardscape, and generally prefers biological and mechanical control over chemicals.

Sources: The 2Hr Aquarist, How to get rid of brown algae (diatoms) and How to control algae without algicides (www.2hraquarist.com www.2hraquarist.com); Tropica Plant Guide, Types of algae (tropica.com).