The absolute minimum size tank for a betta fish is 2.5 gallons with a heater and filter, although if you have a bigger tank, you don't have to do as many water changes. Despite the recent fad of keeping bettas in small vases or bowls please do not keep a betta fish in a tank or bowl that holds less than 2 gallons; it is terrible for their Hiding: Stressed bettas will hide more frequently. They will typically hide behind the filter where the current is the weakest. You may also notice that your betta will hide between plants or inside of hideouts. Moving leaves: In planted tanks, a strong current will cause the leaves of most plants to list and sway with the flow of water. Poor water conditions: Clean water is a must for any fish, especially bettas. Low water temperatures: Bettas are tropical fish and need water temps between 75 and 80°F. Overfeeding: Excess food can kill your fish. Harassment by tank mates: Aggression—both from or directed at a betta—can reduce its lifespan. Java Moss is very versatile, growing attached to driftwood, planted in the substrate as a brilliant green carpet plant, or floating on the water surface. This plant makes a great choice for a betta or community tank and is readily available from all good fish stores and online. 24. Anacharis. 3hYp.