Probably the first fish that comes to mind when setting up a desktop tank such as the Fluval Spec is the ubiquitous betta fish. Their popularity for such setups is not surprising; they have big personalities, but stay relatively small and prefer subdued, quiet aquariums. They also come in a wide array of colors and finnage. There are long flowy finned bettas, crowntails, doubletails, short fins, etc. They can be dark blue/black or bright pink or red and just about everything in between. They can be solid colored, dragonscale iridescent or marbled koi patterns. What’s not to love? In the Fluval Spec V, they’re best maintained alone or with a few small tank mates (see our blog Best Tank Mates for Bettas). Although female bettas can be housed together, this setup is not sufficient for a “sorority” tank of multiple females. Having just one male or female betta in the Fluval Spec along with a few small tank mates, however, can still make a rewarding display.
Dwarf rainbowfish in the genus Pseudomugil are another top contender for the Fluval Spec V! They stay small but are often brightly colored and shine like little jewels. Pseudomugil species can be kept in pairs, trios, or small schools. For the Fluval Spec V, a trio makes a nice addition. The male will display to the females almost constantly and they may even spawn amongst the vegetation (unless eggs are pulled, however, you won’t likely see any fry). What’s also nice about these fish is that they readily take crushed flake foods and micropellets, making them easy to keep as far as nano fish go.
In most community tanks, the peaceable catfish in the genus Corydoras are a classic choice for bottom dwelling fish. They make an excellent clean up crew, eating fallen flakes and other bits of food that hit the substrate. However, most Corydoras get a bit large for the Fluval Spec V and prefer to be in numbers that would overwhelm a five gallon tank. The solution lies with the pygmy Corydoras! There are three species that fall under this category, Corydoras pygmaeus, Corydoras hastatus, and Corydoras habrosus. C. pygmaeus is the most commonly encountered and probably the best suited for your new Fluval Spec V tank. Six is the magic schooling number minimum, and you should be able to stock six pygmy cories in the Fluval Spec V with little issue.
When it comes to small and colorful fish, the celestial pearl danio is hard to beat. They almost resemble little trout, with their dark blue base color and white spots (hence pearl). The males of this species have bright red fins and aren’t afraid to strut their stuff. They do better in groups and you can easily stock a school of six in a Fluval Spec V, which will ideally consist of two trios (1 male, 2 female). They also prefer cooler temps in the low 70’s, which means they may not even require a heater to thrive!
Smaller than the already small neon tetra is the green neon, making it especially suited for the Fluval Spec V! The subdued lighting and gentle flow also compliment these fish. They like to school, so keep at least six. Although not as “big” as the more common neon tetra, they are just as beautiful; with a bright blue stripe through the lateral line and green base color with a subtle hint of red. They are not fussy eaters and will accept most flakes and micropellets.
At the top of any nano tank contender list is the spectacular chili rasbora. Maxing out at just 0.5” in size, they easily fit in the Fluval Spec V, with room to spare. The only caveat is that they do require tiny foods (live or frozen being ideal) and can be sensitive to water quality. However, in a cycled nano tank, they stand out with their bright red coloration.
Oryzias woworae, or the Daisy Ricefish, is another great choice for the Fluval Spec V. A bit of an oddball with regard to its breeding behavior, daisy ricefish are a treat to watch in small aquariums. The females look rather plain in comparison to the males, but can be seen with clusters of eggs near the vent when breeding. The males of this species have a brilliant blue coloration with red margins on their fins. At just a little over an inch in size, you can keep a nice group of them in the Fluval Spec V.
Ember tetras are a great nano fish that are readily available at pet stores and fit nicely in the Fluval Spec V in groups of 3-6. They exhibit bright orange coloration in both sexes (though it is more intense in the males). Another great characteristic is that they are not at all fussy about food and will take crushed flake food from the surface of the tank.
An attractive and active choice for the Fluval Spec V is none other than the white cloud mountain minnow. They come in either their natural form or a gold variant and either have short or long fins. White clouds are a very peaceful schooling fish that does better in groups. This fish also does not require a heater and will thrive at room temperature.
Known scientifically as Poecilia wingei, the Endler’s livebearer is a small fish closely related to guppies. They are so closely related, in fact, that they often interbreed. Therefore, it is not recommended that you house the two species together (guppies being Poecilia reticulata). Because they are livebearers, Endler females will birth live, developed young once a month if kept with males. These “fry” are born large enough to accept crushed flake or commercial fry food or baby brine instantly, making them super easy to raise. Although the female Endlers are a drab grey color, the males come in a rainbow of hues and can be housed together with no fuss or fighting. The Fluval Spec V can easily house a few pairs or a group of males if babies are not wanted (breeding is virtually guaranteed with both sexes present).
Information from the manufacturer - https://fluvalaquatics.com/us/spec/