HomeCompare fishDwarf rainbowfish vs Slim betta Dwarf rainbowfish vs Slim betta: can they live together? Verdict: With cautionThe Slim betta can be semi-aggressive or nip fins.The Slim betta grows about twice as long as the Dwarf rainbowfish; watch for bullying or predation.Both are comfortable at 24–28°C (75–82°F).A pH of 6.5–7.5 suits both.Minimum tank for the pair: 150 L (40 US gal)Side by sideDwarf rainbowfishSlim bettaAdult size5 cm (2 in)10 cm (3.9 in)Minimum tank150 L (40 US gal)75 L (20 US gal)Temperature22–28°C (72–82°F)24–30°C (75–86°F)pH6.5–7.56.5–7.5Hardness8–18 dGH (143–321 ppm)5–15 dGH (89–268 ppm)TemperamentPeacefulSemi-aggressiveCommunity tankGoodGoodCare levelEasyEasyDietOmnivoreOmnivoreSpecies profilesDwarf rainbowfishMelanotaenia praecoxSlim bettaBetta bellica