How to Fertilize monk's hood cactus?
Very weak cactus feed once monthly during warm active growth period

monk's hood cactus · Astrophytum ornatum
Under glass grow in a sharply-draining loam based compost (JI No2) with extra perlite or sharp sand or a proprietary cactus compost, in bright filtered light. Water thoroughly once the compost has become dry in the growing season from spring to early-autumn, but keep dry when dormant. In warmer climates outdoors grow in sharply-drained, poor, slightly alkaline soil in full sun
Very weak cactus feed once monthly during warm active growth period