What it looks like
Stiff, grey-green branches, splayed out like antlers – hence the name. Up to a centimeter long, they grow along the edge of leaves, at the filter outlet, and on rocks. They differ from black beard algae in that they grow as individual branched filaments, not dense tufts, and are lighter in color.
Why it appears
The same group of red algae and the same reasons as black beard algae: unstable CO₂, excess organic matter, and constant flow in one spot. They often coexist in the same aquarium.
It's worth checking the filter specifically: staghorn algae particularly likes to settle on its outlet and on surfaces that haven't been cleaned for a long time.
What to do
The procedure is the same as for black beard algae:
- Stabilize CO₂ supply or reduce light if there is no CO₂ injection;
- Clean the filter and remove stagnant organic matter;
- Spot treat with 3% hydrogen peroxide from a syringe with the pump off, 1–2 ml per spot;
- Trim heavily overgrown leaves.
More details on dosages and precautions can be found in the black beard algae analysis: it's the same technique.
Who eats it
Practically no one. Young filaments are sometimes nibbled by Siamese algae eaters, but adult ones are not eaten by any aquarium fish. The only reliable solution here is to eliminate the cause.