What each algae eater actually eats, and why the crew usually disappoints

People buy a cleanup crew expecting it to solve algae and get a mixed result, because the animals are specialists and the label is not.

Who eats what

• Nerite snails. The best general glass and hardscape grazers. They handle the green film and the hard green spots that most animals ignore. They will lay small white eggs on hardscape that do not hatch in fresh water and do not come off.
• Amano shrimp. Excellent on soft hair algae and leftover food. Largely ignore glass. Need to be kept in a group and they are outcompeted for food in a tank with active fish.
• Otocinclus. Very good on soft brown diatom film on leaves, which is the one snails handle badly. They need an established tank with real biofilm or they starve, and they often arrive already thin.
• Siamese algae eater. One of the few that genuinely eats black brush algae, but only while young, and it grows large and gets less interested.
• Bristlenose pleco. Grazes hard surfaces, produces a lot of waste, and needs wood.
• Nobody reliably eats: blue-green bacterial sheets, staghorn, or established black brush algae. Those are handled by fixing conditions, not by animals.

Why the crew disappoints
Algae is a symptom of light and nutrients being out of balance, and animals eat the visible result at whatever rate they eat it. A crew in a tank with too much light on for too long is being asked to out-eat the growth, and it cannot.

The sequence that works: fix the duration and intensity of light first, get the plants growing so they compete for nutrients, then add a small crew to keep the surfaces tidy.