Fish — life-stage care (young/juvenile, adult, senior/older, growth & aging)
Source: first-hand owner-practical care page, saved to source_file; every claim below is a C1 byte-substring of it.
Claims
Some adult fish grow very large, making them unsuitable as pets – for example, some catfish varieties (the red tail, shovelnose, pangasius), giant gourami and pacu.At the beginning, you will need to ‘seed’ the tank with a product to kick-start the growth of bacteria that are essential for keeping your water clean and suitable for fish once they arrive.Healthy scales – smooth, no sign of injury or fungal growthBreeding for exaggerated physical features has a negative impact on welfare, so we discourage the keeping of such fish.
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Source: pdf-raw/companion-care/exotic_rspca_fish.txt · https://www.rspca.org.uk/adviceandwelfare/pets/fish