Arcadia Aquatics
  • Species: Mbu Puffer

  • Species: Clown loach

  • Species: Carinotetraodon travancoricus

  • Species: Channa aurantimaculata

  • Species: Redtail Catfish

  • Species: Symphysodon

  • Species: Tetraodon lineatus

  • Species: Tetraodon suvatti

  • Species: Gymnothorax tile

Fish for experts

09 December 2016


One of the key features of the Tropical Fish Finder website is the database tool that allows you to do a search for a particular fish. The results will not only link to information about that fish such as water chemistry requirements and diet, but also by clicking on the "stock" link that comes up on the results page, you can find out which stores currently sell that particular fish. Some even support online shopping, meaning you can order fish and have them delivered to your door.

In this article we'll be looking at some of the more demanding fish in the hobby, species that aren't routinely sold in aquarium shops but have a lot to offer the expert fishkeeper. Some of these are considered among the crown jewels of the hobby, supremely desirable species that need skill and experience to keep well. Others are simply difficult and delicate fish that place very particular demands on the aquarist in terms of diet, water chemistry or aquarium size. Either way, these fish will be ones that many hobbyists will aspire to keeping at some time or another.

Red Tailed Catfish, Phractocephalus hemioliopterus

The notorious but much-loved 'RTC' exemplifies one extreme of the fishkeeping hobby, that of the jumbo predatory catfish. Although not demanding in other respects, its adult size makes it very difficult to house properly. Aquarium specimens routinely exceed 1.2 m (4 ft) in length, and these fish are bulky, muscular animals that place heavy demands on the aquarium in terms of swimming space, territory and above all else filtration. Needless to say only the biggest aquaria are suitable: something with many thousands of litres capacity and measuring at least 3-4 metres in length. Filtration would have to be equally massive, with pond-grade canister filters probably the most cost-effective approach. On the other hand, RTCs aren't fussy about food and eat all sorts of fresh and frozen fish and seafood. Soft to medium hard, neutral water chemistry will provide the best balance between their water chemistry demands (they prefer soft water) and optimal biological filtration (filter bacteria don't do well under acidic conditions). Red-Tailed Catfish are very territorial but tolerant of dissimilar (i.e., non-pimelodid) fish too large to be viewed as food, with species such as large Pacu and Thorny Catfish working quite well. Red-Tailed Catfish are very beautiful but rarely seen in aquarium shops for what are probably obvious reasons, but you can occasionally pick them up in stores specialising in large catfish and oddball predators; at the time of writing, this species was in stock at Wholesale Tropicals.

Discus, Symphysodon spp.

At the other extreme are fish that aren't particularly big but for one reason or another aren't recommended for inexperienced or casual fishkeepers. Discus are the classic examples of these, being rather nice aquarium fish in terms of size, colouration and peaceful behaviour. Wild-type fish are very colourful, but Discus have also been bred into numerous very colourful varieties including ones with all sorts of combinations of red, green and blue. However, while potentially excellent community tank residents, Discus do place a few key demands on the fishkeeper. For a start, soft water is more or less essential. To be fair the farmed specimens are less demanding than wild-caught specimens, but that still means you're aiming for hardness around 1-12 degrees dH, pH 6-7.5. Discus won't do well in 'liquid rock' hard, alkaline tap water of the sort supplied to aquarists across many parts of the UK. Discus also need warmth, 28-30 degrees C (82-86 F), quite a bit above normal for community tanks. This also means oxygen levels in the water will be lower than usual, so the tank mustn't be overstocked. Discus are very intolerant of poor water chemistry; as usual, zero ammonia and nitrite levels are needed, but nitrate levels should be as low as practical, ideally 20 mg/l or less. This invariably means more frequent than usual water changes, with many experts recommending water changes of 20-30% every day or two. If you're up to the challenge, Discus can be very rewarding. They're exceptionally pretty fish and get along well with very peaceful, warmth-tolerant community fish such as Corydoras sterbai, Rummynose Tetras, Cardinal Tetras and Silver Hatchetfish. Mixing with Angelfish is not recommended though as Angels tend to bully them and often carry germs that cause serious health problems for Discus. Most of the larger aquarium shops carry selections of Discus; at the time of writing these included such retailers as Aquahome Aquatic Centre, Maidenhead Aquatics @ Crowland and Wildwoods. It's worth checking with them what the ambient water chemistry is before purchasing so that you can ensure your home aquarium has similar conditions; while farmed Discus are a bit more adaptable than wild ones, they still don't like dramatic changes in water chemistry.

Snakeheads, Channa and Parachanna spp.

At one time Snakeheads were the 'bad boys' of the hobby because the most commonly traded species as Channa striata, a species normally reared for food and well able to top 1 m (over 3 ft) in length. Juveniles are prettily marked with red and black stripes, but the adults are rather nondescript greenish-grey fish with massive appetites are violent personalities. But over the last twenty years their reputation has changed dramatically thanks to the importation of many dwarf species such as Channa aurantimaculata and Channa stewarti that combine moderate size (20-40 cm) with attractive colours at all stages of their life cycle. Snakeheads are not too difficult to keep, but as with all predatory fish they do place certain non-negotiable demands on the keeper. To begin with, a varied diet is essential. Prawns and mussels are cheap but vitamin-B1 deficient, so have to be used sparingly, with other, more rounded food items like earthworms, gut-loaded river shrimp, frozen lancefish and cockles offered instead. Some specimens may be reticent about taking non-living foods; it's worth looking for a retailer who has their Snakeheads weaned onto frozen foods before you buy, though training them to do so isn't hard. Snakeheads are generally adaptable with regard to water chemistry, but the dwarf species in particular frequently favour the lower end of the temperature range, so it's important to check this aspect before setting up the aquarium. Snakeheads typically territorial and predatory so are normally kept on their own, but mated pairs can work, and in some cases tankmates of similar or larger size may work, for example L-number catfish. Snakeheads are not widely traded, but retailers who specialise in predatory fish do get them in stock from time to time. Snakeheads are a speciality of Wildwoods though, and that's a good place to track down the rarer varieties in particular.

Pufferfish, family Tetraodontidae

Puffers are popular with beginners, but unfortunately they are quite difficult to keep well. Many species require brackish water, in particular the Figure-8 Puffer, the Ceylon (or Topaz) Puffer, and the Green Spotted Puffer. Others are large, predatory or both; examples of these include Tetraodon mbu, Tetraodon fahaka and the various 'Target Puffers' like Tetraodon leiurus and 'Lurker Puffers' like Tetraodon suvattii. While there are some dwarf species, including the popular Dwarf or Pea Puffer Carinotetraodon travancoricus, even these are relatively nippy and territorial fish for their size, unsuitable for community tank situations. Even the South American Puffer has its flaws; while small and peaceful towards its own kind, it can be a fin-nipper and its fast-growing teeth demand a crunchy diet of snails otherwise dental work will be required. Nonetheless, pufferfish are generally hardy fish provided water chemistry and quality are good, and if the aquarist is willing to set up a tank just for them (which is almost always essential) they aren't that hard to keep. Research pays dividends here, and the Tropical Fish Finder database will be a good place to start finding out about a pufferfish before you buy it.

Freshwater Morays

Two or three species have been traded under this name, but the commonest species is Gymnothorax tile. Despite often being sold as freshwater fish, these moray eels are brackish to marine fish that inhabit estuaries and tidepools rather than freshwater rivers. When kept in freshwater conditions for too long they invariably get sick, the first sign of which is a refusal to feed. As with many other brackish water fish the precise salinity isn't too critical, and anywhere between SG 1.005 and 1.015 will do, alongside good water quality and a high level of carbonate hardness to inhibit acidification between water changes. Moray Eels are fairly peaceful but hunt for small fish and shrimps using their acute sense of smell. In fact their eyesight is poor, and there are some reports of them snapping at tankmates far too large to have been eaten. So while they have been kept with things like Scats and Monos, the ideal is probably to keep Morays on their own, either singly or in groups. Feeding is not normally a problem as all sorts of frozen foods are taken including white fish fillet and pieces of seafood, but they are good escape artists and a common source of mortality is an ill-fated attempt to slither out of the aquarium. A heavy, secure hood is therefore essential. Morays are periodically seen in many of the large aquarium shops; at the time of writing this included Wholesale Tropicals and Woodford Aquatics.

Clown Loaches, Chromobotia macracanthus

While a spectacular fish in many ways, the Clown Loach gets much larger than many beginners assume, making it a poor choice for the average community tank. Adult specimens easily reach 20-25 cm (8-10 inches) with some specimens getting even bigger. They are also highly social fish, and honestly shouldn't be kept in groups smaller than 5 specimens. Obviously a large number of big fish will place a heavy demand on the aquarium and its filter, so a spacious tank (upwards of 450 litres) together with one or more heavy-duty canister filters will be needed. Water chemistry isn't a crucial factor, though softer water conditions are preferred. However, water quality must be excellent, and Clown Loaches are notorious 'canaries' in the sense of being among the first fish to get sick when conditions deteriorate. All this aside, Clown Loaches are fairly peaceful by loach standards, and work well with robust midwater community fish like rainbowfish, barbs and the larger tetras. They also cohabit well with non-aggressive cichlids. Being such popular fish, Clown Loaches are sold by most retailers, including Aquatic Design Centre, World of Water @ Romsey and World of Water @ Manchester.