Max Size: 1cm

Ruby Rasbora (Paedocypris progenetica)

Prior to 2012, when the tiniest frog was discovered, the Ruby Rasbora held the title of smallest known vertebrate. The Ruby Rasbora still holds the world-record title for being the smallest freshwater fish capable of living in a home aquarium.

Since Ruby Rasboras are incredibly fragile and require such low water acidity, even if you are experienced in fishkeeping, these are expert-level fish and should not be kept by beginners. Also, these fish do not tolerate elevated nitrates or fluctuations in water chemistry, so be sure to acclimate them carefully.

A decent-sized group of 12 or more will help give these peaceful fish confidence since they can be pretty timid. The best aquarium is a species-only aquarium, but if you plan to keep other aquatic species with them, make sure they are also small and serene. For example, Neon Tetras, Micro Rasboras, small Caridina and Neocaridina shrimps are all suitable tankmates.

Small aquariums with heavy plants are ideal for Ruby Rasboras. In addition to mature water and dense vegetation, there should also be floating plants that diffuse light and create numerous hiding places. Broad-leaved plants can encourage spawning, and filtration should be effective, but water movement should be gentle.

It is highly recommended that RO water is used and that this is filtered through aquarium peat to reduce the pH. It may also be beneficial to add dried Indian almond leaves or blackwater extract. As a result of the tannins released, the water will have a natural tea colour. This won't harm the fish but will allow them to show their most vibrant colours.

A Ruby Rasboras body is thin and somewhat transparent with rather peculiar pelvic fins with clutching pads that males use to hold the females during mating. Spawning males will become a crystal red colour and will display a red mark on their heads that are used as a blinking light to lure the females to the spawning ground.


Ruby Rasbora
Quick Facts
Scientific NamePaedocypris progenetica
Year Described2006
Other NamesIndonesian Superdwarf fish, Sumatran Miniature Cyprinid
Aquarium LevelMiddle
DifficultyIntermediate - Advanced
Best kept asGroups 10+
Water Parameters
Water TypeFreshwater
PH3.0 - 4.0
GH0 - 5
80 - 89℉
26.7 - 31.7℃


In the home aquarium, the Ruby Rasbora will readily accept most good quality dried foods such as granules, flakes and sinking pellets. These modern food products have been developed to provide all adequate nutrition to maintain your fish's health and dietary requirements.

Providing additional foodstuffs such as live, frozen, and freeze-dried meals such as bloodworm, daphnia, and tubifex once or twice a week will provide additional benefits to your fish's health and well-being but is not a must for this fish.

It should be noted that bloodworms should only be given as an occasional treat and should not be used as the staple diet as they are difficult for fish to digest and can potentially cause blockages.

This fish is an omnivore in the wild, meaning it will consume some vegetable matter. Although most modern fish foods take this into account and include them in their products, you can still supplement your fish's diet with blanched vegetables such as spinach, broccoli, and zucchini. Ensure you do not overfeed your fish and remove any leftovers the following day.

Sexual Dimorphism

Differentiating a male and female Ruby Rasbora is relatively straightforward. In males, the pelvic fins are highly modified, with hypertrophied muscles and a keratinised pad in front. The female pelvic fins, on the other hand, are rudimentary or absent, and they also grow more significant than the males.

Other Rasboras of interest

Black Line Rasbora(Rasbora borapetensis)
Blue Line Rasbora(Rasbora sarawakensis)
Chilli Rasbora(Boraras Brigittae)
Clown Rasbora(Rasbora kalochroma)
Dwarf Rasbora(Boraras maculatus)
Emerald Eye Rasbora(Brevibora dorsiocellata)
View all Rasboras
Date Added: 22/09/2022 16:54:03 - Updated: 27/09/2022 13:02:09