A 5-gallon tank is the smallest defensible heated, filtered freshwater setup - and stocking is limited. Best options: 1) one male betta + a couple of nerite snails. Add live plants, soft sponge filter, 25W heater. 2) cherry shrimp colony - start with 10-15 shrimp + 3-5 nerite snails. They reproduce; expect 50-100 in 6 months. 3) chili rasbora micro-school - 8-10 fish maximum. Nano peaceful fish handle the small footprint. 4) Endler's livebearer trio (1 male + 2 females, separate juveniles to avoid overstocking). What does NOT fit: goldfish (need 30+ gallons; common goldfish 75+), neon tetras (need 6+ in 10g+), guppies (need 10g+ for single trio), platies/swordtails, all gouramis except scarlet badis, all plecos, all corydoras, all African cichlids. Aquascape considerations: short footprint = limited substrate depth. Use small driftwood + small leaf litter for bettas. Foreground carpets need 2-3" substrate at minimum. Do NOT skip the heater: 5 gallons swings 5-8°F in a single day with room-temp heating cycles. 25W mini Hydor or Eheim Jager. Do NOT skip the filter: sponge filter on USB pump or a small HOB rated for 10g (oversized = better). Cycle for 3-4 weeks before adding livestock - small tanks crash fastest under uncycled conditions.
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