50 Ways to Kill Your Fish: Buy Sick Fish

This advice may sound obvious, but buy the healthiest fish you can. When you go to the pet store, don't let the employee choose any ol' fish that ends up in the net. I used to stand in front of the shop tanks and stare at the fish forever until I was sure of which ones I wanted... the most lively, engaging, beautiful creatures possible!

What Are the Signs of a Healthy Fish? (aka How Can I Tell If My Fish Is Sick?)

It can really depend on the species, but here are some general guidelines of what to look for:

• Appetite: Healthy fish are always looking for food, so loss of appetite is one of the first telltales that something's wrong. Don't be afraid to ask an employee to feed the fish as proof of their hunger. This is especially useful for species that are notoriously picky eaters.
• Swimming Ability: You should be able to immediately spot any fish that are having difficulty swimming, can't stay upright, or keep bumping into things.
• Energy Level: Lethargic fish with no energy can be a sign of illness (or they could be sleeping). Conversely, swimming quickly or erratically can be a sign of distress.
• Breathing: Look out for fish that keep gasping for air at the surface or have unusually rapid gill movement. 
• Outlier Behavior: Remember that Sesame Street game "One of these things is not like the other"? Yeah, don't pick the oddball. If this fish is alone and it's supposed to be schooling fish, just say no. If it's hovering near the water surface or sitting at the bottom (and that's not usual for the species), then beware. If it's an overly aggressive fighter or an overly shy wallflower hiding behind the filter for a long time, it may be way stressed out.
• Imperfections: This isn't a comprehensive list, but some common signs include...
• Wounds: ragged or white burns on fins and tail, short barbels, holes, missing scales
• Discoloration: faded color, white patches, cloudy eye, stress bars, inflamed gills
• Parasites: white or gold spots, worms in poop or gills
• Deformities: scales that don't lay flat (like a pine cone), swollen eyes, crooked back or tail

I'll give you an example. Our new turquoise and yellow betta suddenly died while in quarantine, so I wanted to replace him with another turquoise and yellow betta. There was a beautiful one that looked very similar to our original fish, but he just seemed... not very responsive. I know bettas in cups don't have a lot of room to move, but still. On the other hand, there was another all-blue betta who wasn't maybe as striking, but was very responsive and lively. I chose to go with personality and health over appearance, and I'm happy to say he's just as dynamic and charming as the day we got him. (o˘◡˘o)

In the King of DIY's How to Keep Discus video, the speaker recommends starting with obviously healthy stock because a poor quality fish will not magically turn into a beautiful specimen. That advice of course all depends on your goals in fish keeping. There are some people who like to rescue sickly bettas (or other animals) from stores or friends. There are numerous amazing transformation pictures posted online, so good care can definitely go quite a ways. However, just be aware that if you choose to go that route, that's no guarantee of success because you are starting off at a disadvantage. It's going to take a lot of effort, time, and money to potentially bring your patient back from the brink of death.

I always enjoy seeing successful betta rescue transformations. (Source: Reddit)

Picking happy, healthy creatures is going to give you the best leg up in, well, not killing your fish. Hopefully now you'll know what to look out for. Good luck and keep on swimming!