Neon Tetras (Paracheirodon innesi) may make good tank mates for your male Betta if the circumstances are right. The basics for success are already there. Both neons and bettas enjoy similar water parameters. They thrive in a tropical tank with a slightly acidic pH, soft to moderate hardness and a temperature between 75F – 79F [24C - 26C]. Neither bettas nor neons do well when exposed to ammonia or nitrite and neons are especially sensitive to poor water quality so a cycled tank is a must.
The most important thing to address with neon tetras are their social structure. Neons are a shoaling species and must be kept in groups for long-term success. Schools smaller then 6 tend to suffer stress induced illnesses so plan on keeping several at a time. In a 10 gallon [38 liters] with one male betta you can safely keep 6 – 8 neons with good filtration and weekly partial water changes.
If you are looking to house your neon tetras with a male betta specifically, there are a few other things to consider as well. First, it’s best to avoid adding neons to a tank with a betta who is known to be overly aggressive. As you probably know, individual male and female betta personalities can range from the timid to the outright belligerent. If your betta has a bad reputation you may want to concede to his desire to go solo. Even if your betta is willing to play nice with others, it is highly recommended to choose only individual neons of a healthy adult size. Very young or small neons have a habit of being confused with dinner. Aim for companions that won’t fit in your betta’s mouth.
When choosing neon tetras, look for fish that are swimming with the group, have vibrant coloration and are all around healthy in appearance. Avoid fish that may be hiding, lethargic, showing signs of disease or are misshapen. Neons are notorious for not shipping well so ask your LFS when they arrived. If they just came in, give them a couple of days to develop any illnesses. Neons are very prone to Ich and Neon Tetra Disease. Aquarists are cautioned to quarantine new fish for a minimum of 4 weeks but it is emphasized even more so with this species. Because a change in water parameters fuels stress induced illnesses, It’s recommended to acclimate them to their quarantine tank using the water from the Betta tank that will ultimately be their final destination. This way they aren’t exposed to the stress of acclimating to the store water, the quarantine tank water and then the final aquarium water all within a month.
Neons are gorgeous little fish and are fascinating to watch. Personally, they are favorites of the common shoaling fish and look absolutely amazing in a tank with dark substrate and live plants.