Cichlids + many marine fish defend territory. Normal in moderation. Provide sufficient hiding spots + visual barriers.
Single male with multiple females = peace. Multiple males with one female = constant fighting. Adjust ratios.
Too many fish in too little space. Tank under-stocked = peaceful, over-stocked = chaos.
Pair-bonded fish defend eggs/fry violently. Sometimes need to remove other tankmates.
Cichlids + community fish = mismatch. Always research compatibility before adding.
Test water first - many "behavior" issues are actually water-quality problems. Use the water parameter checker to score your test results, the disease symptom matcher if you observe physical signs, or the general diagnoser to narrow further. Browse the disease database if illness is suspected.
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