Profiles with adult tank sizes, temperament, and FAQs. Filter by water type or difficulty.
Showing 9 species · Intermediate
Freshwater · Intermediate
Paracheirodon axelrodi
Cardinal tetras (Paracheirodon axelrodi) are Amazon schoolers with a full red stripe from snout to tail. Plan a school of eight to ten in a planted 20-gallon with soft, clean water, not a neon-sized squeeze in a 10.
Min. tank: 20 gal
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Freshwater · Intermediate
Hemigrammus bleheri / H. rhodostomus / Petitella (trade mix)
Rummy-nose tetras sold in shops are a trade mix of Hemigrammus bleheri, H. rhodostomus, and Petitella names. Care is the same lane. Adults reach about 2 inches. How many fit in a 20-gallon? Eight to ten in a 20-gallon long, and ten still leaves room for six peppered cories on the bottom. Plant it well and keep the water soft to moderate and clean. A bright red nose and black-and-white striped tail are the ID. A pale nose often means stress, a new tank, or dirty water.
Min. tank: 20 gal
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Freshwater · Intermediate
Carassius auratus
Goldfish are coldwater carp, not bowl ornaments. Fancy strains need tens of gallons and strong filtration; single-tail commons belong in very large tanks or ponds.
Min. tank: 30 gal
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Freshwater · Intermediate
Pterophyllum scalare
Freshwater angelfish are tall Amazonian cichlids. They need height more than a long, low tank. About 30 gallons and 18+ inches of height for a pair is an indoor start.
Min. tank: 30 gal
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Freshwater · Intermediate
Carinotetraodon travancoricus
Pea puffers (Carinotetraodon travancoricus) are freshwater puffers from southwest India that top out around an inch. One fits a heavily planted 10-gallon. A small group needs a 20 long or larger with plenty of plants. Keep them at 74 to 80°F on frozen foods and snails, in a tank with no shrimp or long-finned fish.
Min. tank: 10 gal
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Freshwater · Intermediate
Otocinclus spp.
Otocinclus (Otocinclus spp., often O. vittatus in the trade mix) stay about 1.5–2 inches. A school of 6+ belongs in a 20-gallon that has been running months with algae and biofilm, not a new 10-gallon sucker hire.
Min. tank: 20 gal
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Saltwater · Intermediate
Amphiprion ocellaris
Ocellaris clownfish are among the more forgiving marine fish, but they still need a cycled saltwater tank, stable salinity, and marine-level testing. A 20-gallon tank can house a pair; 30 gallons is more comfortable.
Min. tank: 20 gal
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Saltwater · Intermediate
Zebrasoma flavescens
Yellow tangs are active Hawaiian surgeonfish that need swimming room, not a nano reef. A home-aquarium minimum is about 125 gallons with length to patrol and rock to graze.
Min. tank: 125 gal
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Saltwater · Intermediate
Nemateleotris magnifica
Firefish gobies are elegant, hovering dartfish for a covered saltwater tank. A 20-gallon reef can work for one. The lid is not optional. They jump.
Min. tank: 20 gal
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