A variety of topical fish, snails and shrimp are sold as algae-eaters for the freshwater aquarium. Most of these and invertebrates only eat green algae, ignoring blue-green algae completely and having a marginal effect at best on red algae and diatoms.
Freshwater Frenzy: Best Fish for a Cold-Water Aquarium.
The best fish for cycling a new freshwater aquarium are hardy minnows, such as . Besides being robust, these fish are also lively and constantly on display. Because they are so active, it makes it easier to spot signs of disease and anomalous behavior. Happy danios will be swimming about in midwater, greedily consuming whatever small amounts of food you give them. Stressed danios are skittish, disinterested in food, and often appear to be breathing heavily and may even gasp at the surface if conditions are really poor.
10 Most Colorful Freshwater Fish | Home Aquaria
Other fish suitable for cycling a freshwater aquarium include nonfancy guppies, Corydoras paleatus, C. aeneus, X-ray tetras, pupfish and some of the hardier labyrinth fish, such as banded gouramis and paradisefish. In coldwater tanks, small goldfish work well, but fancy varieties are best avoided in favor of the hardier comets, shubunkins and standards.
Beginner Fish: Tropical Fish for Beginners in Freshwater Aquariums