Top 5 Aquarium Fish That Love Soft Water

Most beginners in the fishkeeping hobby are not aware that not all fish can live in their tap water. Some species are quite sensitive and will only thrive if the pH and GH (or general hardness) of the aquarium match their native habitats. Try measuring the pH and GH levels in your tap water using a multi-test strip. If you have a GH number that is 4 degrees (75 ppm) or lower, then your water contains fewer minerals (e.g., calcium and magnesium) than normal. Rather than fight your naturally soft tap water, consider keeping South American fish and other animals that come from soft water environments.

1. Discus

Symphysodon genus

The “king of the aquarium” is of course the majestic discus, a South American cichlid that can grow to the size of a 5- to 7-inch (13–18 cm) saucer plate. They have been linebred to display a wide assortment of intense colors and unique patterns — such as blue diamond, red turquoise, pigeon blood, checkerboard, albino, snakeskin, and many more. They are generally calm and peaceful for a cichlid but can get territorial when breeding, so get a group of six in a 75-gallon fish tank or larger to minimize any squabbling. While they come from low pH and GH waters in the wild, we have found that in captivity, they can live in pH as high as 6.8–7.6 (if you don’t plan on breeding them) and very soft to moderate GH. It is more important to maintain a higher temperature of 84–86°F (29–30°C) and keep the water parameters as stable as possible. Because of their tiny mouths, feed them a variety of little foods, such as Hikari Vibra Bites, frozen foods, and live brine shrimp. For more details on appropriate tank mates and water change schedules, read the full article.

2. Crystal or Bee Shrimp

Caridina cantonensis

If the discus is too large for your liking, try the Taiwan bee shrimp. This little crustacean has been linebred and hybridized to create countless varieties in all the colors of the rainbow, including King Kong, blue bolt, galaxy pinto, and crystal red shrimp. They are similar in size to the 1.5-inch (4 cm) cherry shrimp or Neocaridina davidi, but usually they are pricier and pickier about their water parameters. Since most fish cannot resist the taste of baby (and adult) shrimp, use a mature aquarium that is 10 gallons or larger for a species-only, breeding setup. To keep a consistently low pH and GH, serious shrimp keepers recommend using an active buffering substrate and RODI (reverse osmosis deionized) water that is dosed with bee shrimp-specific minerals. Aim for a temperature of 68–75°F (20–27°C), pH below 6.8, low KH, and 4-7° (70-130 ppm) GH, but just to be safe, ask the seller what conditions they kept the shrimp in. As nature’s little scavengers, bee shrimp are not picky eaters and will eat all sorts of fish foods and blanched vegetables. However, don’t forget to provide some specialized shrimp foods that have added calcium and minerals to promote healthy molting. For more information, see this overview of freshwater dwarf shrimp.

3. Ram Cichlid

Mikrogeophagus ramirezi

Another spectacular, soft water species is Mikrogeophagus ramirezi. The male is brightly colored with a spiky dorsal fin and feisty personality. They have been carefully bred to display several color variations (e.g., German blue, gold, electric blue, and black) and different body shapes (e.g., regular, long fin, and balloon). Like the discus, this dwarf cichlid is found in South America and prefers warmer, softer waters. We find they do best at temperatures of 84–86° (29–30°C), pH between 5–8, and soft water. A 10-gallon tank with a sponge filter is sufficient for a breeding pair, but upgrade to a 20-gallon or bigger for a community setup. Provide plenty of hiding spots and obstacles to break line of sight and reduce any aggression. Just be aware that they like to dig in substrate and may uproot your plants, so consider using plants like java fern and anubias. Ram cichlids are not finicky eaters and should feed a mixed diet of fish foods, such as flakes, sinking pellets, freeze-dried brine shrimp, and frozen bloodworms. Read the full care guide to learn about appropriate tank mates and breeding practices.

4. Pygmy Cory Catfish

Corydoras pygmaeus

This adorable, 1-inch (3 cm) cory catfish is the perfect midwater to bottom dweller for your next planted tank. How can you not love those big, black eyes, bold horizontal stripe, and tiny barbels that look like a little mustache? While they can technically fit in a 5-gallon aquarium, we recommend getting a 10-gallon tank or larger so that you can get a bigger school of at least 8-12 pygmy corydoras. They originate from the Amazon River basin in Brazil and would prefer lots of live aquarium plants, driftwood, and natural stone to perch on and hide amongst. They can live in temperatures of 72–78°F (22–26°C), pH between 6.4–7.5, and moderately soft water, but make sure to check the parameters used by the breeder or fish store since they can be sensitive to sudden changes. As per their common name, the pygmy cory is fairly small, so keep them with other peaceful nano species, like neon tetras, chili rasboras, celestial pearl danios, or even a chill betta fish. They tend to feed off the ground or other horizontal surfaces, so offer tiny, sinking foods they can swallow whole or rasp on. Their favorite foods include Repashy gel food, baby brine shrimp, daphnia, nano pellets, and tubifex worms. For more details, read our article on pygmy corydoras.

5. Brunei Beauty or Spotfin Betta Fish

Betta macrostoma

Tired of the traditional betta fish (or Betta splendens) sold in mainstream pet stores? This gorgeous, “wild type” betta grows to a hefty 3.5–4 inches (9–10 cm) long and has a long, tubular body with a shorter tail. The male has an orange-brown body with fins that have colorful striping and electric blue edges. They come from the island of Borneo, where the waters are tinted with decaying leaves and other botanicals that greatly soften the water and acidify the pH to levels of 4–6 (although captive-bred specimens can usually live in pH between 6–7). To simulate their native environment, keep the temperature at 74–80°F (23–27°C), dim the lighting, add catappa leaves, and use lots of floating plants and a dwarf aquarium lily for extra shade. Unlike the more aggressive B. splendens, a male and female pair can be kept together in 10-20 gallons of water, but use a bigger tank if you plan on getting a small group or other tank mates. Feed them plenty of small, meaty foods with some roughage, such as floating betta pellets, daphnia, and brine shrimp. “Macrostoma” is Latin for “big mouth,” which the male uses to hold the fertilized eggs until the young have hatched and are free-swimming. To learn more about their breeding habits, check out our article on wild bettas.

Final Thoughts on Soft Water

In general, it is easier to take soft water and add minerals to increase the GH, but it is more difficult to take hard water and lower the GH. Plus, soft water can be a little dangerous —low GH is often paired with low KH (or buffering capacity), and low KH can lead to pH swings or crashes that adversely affect the fish. You can soften water by using catappa leaves, minimal water changes, RODI water, and other methods described in our water chemistry article. However, if you have naturally hard water coming from the tap, read our blog post on Top 10 Aquarium Fish That Love Hard Water for more fish stocking ideas.