The aquatic frogs most commonly sold in pet shops are the African Clawed Frog (Xenopus laevis) and African Dwarf Frogs (various species of Hymenochirus). All are fully aquatic in the sense of never needing to leave the water. But like other amphibians, they still breathe air, and if the aquarium is too deep, they will drown.
In general terms aquatic frogs are very easy to care for. They are largely indifferent to water chemistry, and tank-bred specimens readily take a variety of live, frozen and even dried foods.
But aquatic frogs do have certain requirements that cannot be ignored, specifically their need for a reasonably spacious aquarium, heating, and filtration. Most of the problems people have with aquatic frogs come down to keeping them in aquaria that are too small, too cold, or inadequately filtered.
How to identify your aquatic frog
The African Clawed Frog (Xenopus laevis) can be immediately recognised by comparing its front and back feet. Its front feet are not webbed, whereas its back feet are webbed. The three middle toes on their back feet are equipped with short black claws, hence their common name. African Clawed Frogs are quite big animals when mature, with a body length of 8-15 cm (3-6 inches). Wild-type African Clawed Frogs are mottled green, but the albino forms are widely sold as well. A second species, Xenopus tropicalis, is widely used as a lab animal, and may turn up in pet shops occasionally. It is about half the length of Xenopus laevis, and also much darker in colour.
African Dwarf Frogs are most commonly Hymenochirus boettgeri though Hymenochirus curtipes is occasionally traded as well. Unlike the African Clawed Frog, these frogs have webbing on both their front feet and their back feet. They are also much smaller, adult size being less than 5 cm (2 inches). Telling Hymenochirus boettgeri apart from Hymenochirus curtipes is not easy, but Hymenochirus curtipes is said to have rougher, more warty skin.
Too many aquarists attempt to keep these interesting frogs in aquaria that are far too small for them.
For practical reasons, you should not bother with a tank less than 24-37 litres (6-10 gallons) in size. Smaller tanks will be too difficult to heat and filter adequately, and smaller tanks are also less forgiving of mistakes and neglect. If nothing else, a reasonably large aquarium will give you space to keep multiple frogs in a richer, more interesting environment decorated with rocks and plants.
It doesn't matter whether you buy a plastic or glass aquarium, provided it has sufficient capacity. But do choose an aquarium that is shallow and wide, since these frogs don't like deep water.
A viable small aquarium for African Dwarf Frogs would be one measuring 20 cm by 20 cm by 60 cm (8 x 8 x 24 inches). Such an aquarium would have a volume of about 24 litres (6 gallons) and could accommodate 3-4 African Dwarf Frogs without any problems provided it was adequately heated and filtered. A bigger aquarium would allow you to have more frogs, and above 37 litres (10 gallons), you have the option to add some fish as well.
Being rather bigger, African Clawed Frogs will need more space. Because they are quite messy animals, 37 litres (10 gallons) is really the absolute minimum, and that would be acceptable for two specimens, assuming adequate heating and filtration. Allow another 15-18 litres (4-5 gallons) per additional specimen.
What about the plastic frog habitats sold in malls, department stores, science shops and other places not otherwise focused on pets? Without exception these are overpriced rubbish, so save your money.
Things are a little complicated here, so it's important to identify your frog carefully. The African Clawed Frog (Xenopus laevis) is a subtropical animal and does well at around 20 degrees Celsius (68 degrees Fahrenheit). As its name suggests, Xenopus tropicalis is a tropical species, and needs to be kept warmer, around 25 degrees Celsius (77 degrees Fahrenheit) being adequate. All the traded African Dwarf Frogs (Hymenochirus spp.) are tropical animals, and they also do well at 25 degrees Celsius (77 degrees Fahrenheit).
To summarise then, you will certainly need a heater if you are keeping either African Dwarf Frogs or Xenopus tropicalis. Whether or not you will need a heater to keep African Clawed Frog will depend upon where you live. In subtropical parts of the world such as Florida and Southern California, a heater will not be necessary, but across most of the rest of the United States as well as most of Europe, a heater will be required for long term success.
When frogs are kept too cold, as would be the case in an unheated aquarium, their metabolism slows down. They cannot digest their food properly and their immune system doesn't work effectively. Because these frogs have been widely used in labs, all of this has been studied repeatedly, so there's no need for aquarists to experiment by keeping them in unheated tanks! If you don't live in the subtropics, then you must use a heater.
Frogs are prone to burning themselves on heaters; fit a plastic heater guard around the heater to prevent this problem.
Along with chilling, inadequate filtration is surely one of the major causes of aquatic frog mortality. Just as with fish, you're aiming for 0 ammonia and 0 nitrite.
The filtration system used needn't be anything complicated, and indeed simple undergravel filters and air-powered sponge and box filters would all be inexpensive and eminently suitable. Once installed, such filters would take care of the ammonia produced by these frogs, while helping to keep the water nice and clear.
Do not keep these frogs in aquaria without a filter. Equally, avoid using a filter that is so powerful the frogs have trouble swimming.
Aquatic frogs are not fussy about water conditions provided soft, acidic water is avoided. The ideal conditions are pH 7-8, 10-20 degrees dH. Do not add salt to the water.
As with fish, regular water changes are essential. Change 20-25% of the water each week, taking care to add dechlorinator to the new water before it is poured into the aquarium. If you're away on holiday, skipping water changes for a week or two will do no harm at all, especially if the tank is of an adequate size, as discussed above.
Do not use water from a domestic water softener.
You'll want a hood of some sort: these frogs can "jump" from the water when alarmed, and the larger Xenopus species are notorious escape artists! Although they can breathe air, these frogs rapidly dehydrate on land, and unless quickly returned to their aquarium will soon die.
Lighting and Ultra-Violet Light
Aquatic frogs do like to bask at the surface, but unlike turtles, they do not need ultra-violet light (specifically UV-B) to do well. So feel free to use whatever lights you want.
As adults these frogs are largely sociable animals that exhibit little aggression or bullying. They can be cannibalistic though, so avoid mixing specimens of radically different size. This is especially true of Xenopus tadpoles.
Floating plants are particularly useful, providing resting places close to the surface where the frogs can bask and breathe. Amazon Frogbit and Indian Fern would be ideal. You will need to provide adequate light though, since floating plants tend to require good lighting if they are to do well. Otherwise, plastic plants can be used instead.
Substrate, rocks and other decorations
When decorating the tank, bear in mind that these frogs have very delicate and easily damaged skins. Do not use anything sharp or abrasive. Smooth silica sand is an ideal substrate. Avoid sharp sands such as Tahitian Moon Sand and Eco-Complete. Also avoid anything like to alter water chemistry, such as coral sand.
Rocks should be smooth, ideally things like water-worn cobbles. Don't use jagged rocks, slates, geodes, etc. Bogwood makes a good alternative, but it can lower the pH if your water lacks sufficient carbonate hardness. If you want to use a lot of bogwood, check that you have a carbonate hardness of at least 3 degrees KH (i.e., your tap water supply is not too soft). If you don't have sufficient carbonate hardness, use artificial ornaments instead.
Frogs don't really need hiding places, and the ideal aquarium would simply have plain sand at the bottom and lots of floating plants at the top. Such an aquarium would satisfy the needs of your frogs while being easy to maintain and clean.
African Clawed Frogs (Xenopus laevis) do not often breed in home aquaria, and most of the specimens sold in pet shops will have been produced by exposing females to particular hormones.
African Dwarf Frogs (Hymenochirus spp.) spawn in home aquaria willingly if given the right conditions. At about nine months old, males will indicate their sexual maturity by singing. Males and females can also be distinguished by their appearance; males are smaller and slimmer than the females, and males also develop a distinctive pimple-like structure behind their 'armpits'.
As with other frogs, males sing to attract mates. Pairs mate with the male behind and above the female, holding onto her body with his front legs. This union is known as amplexus and can last for several hours. In that time the pair will move around the aquarium, the female depositing the sticky eggs on solid objects one at a time, and the male immediately fertilising them.
When first laid, the eggs are clear. They are small: less than 2 mm in diameter. Over the next few hours the eggs turn mottled grey, and 48 hours later the embryo should be visible as a small dark grey speck in the middle of the egg. Infertile eggs go cloudy and often become infected with fungi; these eggs should be removed to prevent fungus spreading to healthy eggs.
Over the next two days, the embryo will rapidly develop and quickly resembles a tadpole. Hatching normal occurs by the end of the fourth day. They immediately start feeding, and the tadpoles can be fed liquid and powder foods sold for baby fish.
Although adult frogs will not harm their eggs, they may eat free-swimming tadpoles, so it is best to rear the tadpoles in their own aquarium or a floating breeding trap. Eggs are easily damaged though, so care should be taken when moving them; use a pipette to move individual eggs, not your fingers or forceps.
The tadpoles are relatively easy to rear, but they are sensitive to poor water quality. Just as with rearing baby fish, the aquarist needs to balance the tadpole's requirement for two or more small meals per day against the need to maintain good water quality. Proper filtration and regular water changes are the keys here. Aim to perform small (5-10%) water changes each day for at least the first couple of weeks. Ammonia and nitrite should both be at 0 mg/l, and nitrate levels should be as low as practical.
African Clawed Frogs (Xenopus laevis) are opportunistic predators that consume a wide variety of prey. In aquaria they do particularly well on invertebrates such as earthworms through aquatic insects like mosquito larvae are also enjoyed. The main issue with African Clawed Frogs is to avoid overfeeding them: for an adult, something the size of a large earthworm every other day would be ample. Juveniles can be fed a little more frequently, but it is still important to skip feeding them once or twice a week.
African Dwarf Frogs (Hymenochirus spp.) are also carnivorous, but their prey are generally much smaller. Live foods are favoured, in particular daphnia, brine shrimp, small or chopped earthworms, bloodworms and mosquito larvae. Avoid live tubifex worms though; these come from notoriously dirty habitats and can introduce pathogens of various types. Wet frozen foods are also readily taken. A selection of tubifex, bloodworms, blackworms and glassworms would make an ideal staple diet for these frogs. Blister packs can be kept in the freezer for at least three months without substantial loss of nutritional value.
As with Xenopus frogs, it is important not to overfeed African Dwarf Frogs. Offer enough that your frog has a gently rounded belly, but doesn't look as if it's swallowed a ball! There's no need to feed African Dwarf Frogs every single day, and indeed skipping meals once or twice a week may be helpful.
What about dried foods such as pellets and freeze-dried bloodworms? These can be used occasionally, but if used regularly, they seem to increase the risk of problems such as constipation. So while pet shops and mall vendors might suggest otherwise, don't buy a frog expecting to keep it healthy on just pellets. You can safely use good quality pellets once or twice a week, but for the remaining meals, use live or wet frozen foods instead. Such foods will provide the fibre these frogs need to stay healthy.
Since frogs cannot chew their food, any food offered has to be "bite size" or they won't be able to swallow it.
The prime reasons people fail to keep frogs alive are chilling, poor water quality, starvation, constipation and physical damage. Chilling can be avoided by using a heater, and poor water quality problems will be avoided by using a filter and performing regular water changes. Always add dechlorinator to new water, and take care not to change too much water at once. Unless you can be sure that the pH and hardness of the new water is the same as the water taken out, restrict water changes to 20-25% per week.
Starvation is usually a problem when frogs are offered the wrong diet or one that is so monotonous the frogs lose interest. Either way, offering a varied diet should avoid this problem. Starvation can also occur when frogs are forced to compete with more active or agile animals, typically fish. In general, frogs are best kept alone in single-species aquaria.
Constipation is usually an issue with frogs fed solely on pellet or freeze-dried foods. It can be avoided by using primarily wet frozen or live foods instead. If your frog is already bloated and you suspect constipation, stop using freeze-dried and pellet foods, and restrict the food offered to high-fibre items instead, namely live daphnia and live brine shrimp.
Physical damage usually happens because the frogs are kept in tanks with jagged rocks or gravel. Replace gravel with smooth silica sand or some other type of lime-free aquarium sand you can confirm is sold as suitable for burrowing fish. Remove jagged rocks, and instead decorate the tank with floating plants, plastic ornaments, water-worn pebbles and pieces of bogwood. Physical damage can also occur when frogs are kept with nippy fish. Again, frogs are best kept on their own, and if you want to add fish to their aquarium, select such companion species very carefully. Finally, avoid handling your frogs: they skin is easily damaged, and once that happens, bacterial infections often follow.
Diseases and treatment
Kept properly, aquatic frogs are generally quite hardy and disease-free, but there are a few specific problems to be aware of.
The most important of these is Red Leg, a general term that describes opportunistic bacterial infections of the skin around the legs and belly. It is broadly similar to the disease aquarists call Finrot, and both can be caused by Aeromonas bacteria that occur in all aquaria, even properly maintained ones. Ordinarily these bacteria do no harm, but if a frog is damaged (for example by rough handling) or stressed (because it is chilled or exposed to poor water quality) then these bacteria can overwhelm the frog's immune system.
As its name suggests, the symptoms of Red Leg include raw or bloody-looking lesions on the legs and belly. It can quickly kill frogs, so must be treated as soon as it is noticed. Under lab conditions Tetracycline is usually used to cure Red Leg, administered orally at 1 mg per 5 grammes of body weight, daily, for five days. Hobbyists can use medications such as Maracyn II (Minocycline) and Maracyn Plus (Sulfadimidine and Trimethoprin) that are added to the water, but these will be less reliable. Dose as for tropical fish, remembering to remove carbon from the filter (if used) and to increase aeration through the treatment.
While Red Leg is often fatal and very difficult to treat, it should be stressed that it can easily avoided by keeping aquatic frogs properly.
Fungal infections can quickly kill frogs if not promptly treated. Fungal infections appear as off-white patches of threads, often rather like tufts of cotton wool. They are frequently associated with wounds, but may also appear when frogs are maintained under chronically poor environmental conditions. Various medications have been used to treat Fungal infections on frogs, but Mardel MarOxy (stabilised chlorine oxides) works well and doesn't harm frogs when used as directed.
Finally, Dropsy is syndrome most commonly associated with poor environmental conditions. Though the precise causes may vary, Dropsy is essentially the build up of fluid inside the abdomen caused by damage to the internal organs. Bacterial infections are likely responsible for this in the majority of cases. There are two aspects to dealing with Dropsy. The first is to kill the bacterial infection, and that requires antibiotic medications such as Maracyn II and Maracyn Plus. Secondly, you need to reduce the swelling, and this can be done by adding one level teaspoon of Epsom Salt to each ten gallons of water.
Can frogs be mixed with fish?
There's no easy answer to this, but the short answer is that frogs are invariably best kept alone. Because African Clawed Frogs (Xenopus laevis) are large, predatory, and need relatively cool water, it is tricky to find suitable tankmates for them among the usually traded tropical fish. So they're almost always kept alone.
African Dwarf Frogs (Hymenochirus spp.) on the other hand are often sold as community tank oddballs. They certainly can coexist with very gentle tankmates; first such as Kuhli Loaches, small Corydoras species like Corydoras habrosus, peaceful midwater fish such as Pencilfish, and surface swimmers like Hatchetfish would all be acceptable tankmates. This does of course assume you have sufficient aquarium space: any of these fish would need to be kept in a properly maintained aquarium at least 37 litres (10 gallons) in size.
On the other hand, fish that are prone to be nippy or aggressive should be kept away from African Dwarf Frogs. This includes most of the more boisterous Tetras and Barbs, as well as Dwarf Cichlids. Fish that would be too competitive at feeding time should also be left out, so it wouldn't be sensible keeping them with the larger Corydoras or Loaches.
All this said, African Dwarf Frogs are much happier and easier to keep when maintained in their own aquarium.
Aquatic frogs are appealing animals that are easy to keep provided their needs are respected. But whatever "the guy" at the shopping mall might suggest, they can't be kept in unheated, unfiltered bowls.