What are common compatibility chart mistakes?
Written by
John Williams
Reviewed by
Prof. David Walsh, Ph.D.The main problem with fish compatibility charts is that folks misread them. Relying entirely on them will land you in hot water if they can't be read correctly. From adolescent fish to adult, aggression between mates, size difference ratios, and the schooling effect are all major problems if not heeded.
Life Stage Oversights
- Juvenile fish show different behaviors than adults
- Angel fish fry coexist peacefully but adults hunt small fish
- Research adult sizes and temperaments before purchasing
Directional Aggression
- One species attacks another without reciprocal aggression
- Example: Barbs nip guppy fins but guppies don't retaliate
- Observe tank dynamics for 72 hours after new introductions
Reverse Pairing Neglect
- Charts list compatibility in one direction only
- While tetras tolerate guppies, guppies may attack tetras
- Verify both pairing directions before combining species
Juveniles vs. adults- shockingly large surprises. Young cichlids appear peaceful while in the store. Once mature, they can be territorial and aggressive. Always do your research and find out the adult size of what you're buying. I learned this one the hard way when my angel fish outgrew their tank mates and started eating smaller fish overnight.
Mouth-size ratios as opposed to a fish's body length. Particularly with Oscar fish, since they will happily swallow anything that fits into their mouth opening! Measure your proposed meal against the overall gaps you leave with the Oscar. Allow 50% more space than the opening of the predator's mouth. This alone will avert some distress to the entrants to the aquarium community on death row!
Schooling requirement is non-negotiable. Tetras require a minimum of six members. Fewer will cause stress and disease (chronic stress is documented). They lose coloration without group security. Always maintain species-specific group size. This simulates natural hierarchies, which will significantly decrease aggression.
Check for reverse pairings on charts. Make sure both directions are checked before adding. Use your quarantine tanks for 72-hour observations. Move decorations so territories are disturbed. These steps prevent problems related to directional aggression. Charts don't ensure that fish will house with each other; compatibility requires tolerance in both directions, not just one.
Read the full article: Fish Compatibility Chart Ultimate Guide
