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Stuck in the middle

The following article is called – Stuck in the middle. A tank without mid-water fish could be pretty boring to watch. Many bottom feeders are nocturnal and spend much of their time hidden from view, and surface active fishes really need to be viewed from side-on or even slightly below to be seen clearly from a distance.

Stuck in the middle
A nice group of mid-water swimming fish can make your tank look active and busy. It also provides something that’s clearly visible from the comfort of your armchair.

Spotting those fish which are likely to swim predominantly in mid-water is fairly simple. Surface feeders have upwardly pointing mouths and bottom feeders have a mouth on the underside of their head, but mid-water fish have a mouth position that’s almost slap-bang in the middle of the head.

This enables them to feed comfortably on things dropping or swimming through the water column, such as insect larvae or crustaceans, as well as from the surface or the substrate.

Thankfully, there are hundreds of different species of fish to choose from. Here are some of the best ones to look out for, and a few that are probably best avoided.


The Harlequin, Trigonostigma heteromorpha, used to be in the genus Rasbora but was moved into this new genus a few years ago. The genus contains several similar fish, all with a pork chop-shaped blob on their flanks.

They’re all excellent community fish but need good, clean water and peaceful tankmates. Look out for the pretty T. espei, which has a longer, narrower pork chop shape, and T. hengeli, which is a smaller species.

These usually cost between £1 and £2 each and should be kept in a group of six or more. They grow to a few centimetres in length and will mix with most small, peaceful fishes.

Some benefit from softer, acidic water, so check with the shop before you buy them.

Greater scissortail, Rasbora caudimaculata

The Greater, or Giant, scissortail can reach about 15cm/6″ and needs to be kept in a group of four or more. As a result you’ll need to have a fairly big tank (120cm/4′) to keep these fish comfortably.
They mix well with most other community fish, usually leave plants well alone and develop attractive colours as they get older. Newly imported fish can be prone to bacterial infections, so only buy fish that have been quarantined.


Aquatic retailers often have a tough job trying to convince customers to buy rainbowfishes because they’re one of the ugly ducklings of the fish world. Many of them can look rather uninspiring when they’re young but develop stunning colouration when adult, and unless you’ve got an enthusiastic dealer with the power to persuade you to buy them, or a little imagination of your own, you could miss out on some of the most attractive community fish available.

There are loads of different species of rainbow, but less than a dozen of these are commonly available in the shops.

Rainbows are peaceful mid-water and surface feeding fish and mix well with most other community species. They also come in a range of sizes, from the diminutive Threadfin rainbow to the slightly larger Neon dwarf right up to the comparatively large Red and Boesemani rainbows.
All rainbowfishes fare best when kept in small groups and spend the majority of their time swimming around in mid-water.

Threadfin rainbow, Iriatherina werneri

This tiny species from New Guinea and northern Australia reaches only a few centimetres in length, so it’s fine for those with smaller tanks. The threadfin tag comes from the males, which develop very long extensions on their dorsal, anal and caudal fins.

They’re pretty little fish but really need to be kept in a group containing a mixture of sexes to get them looking their best.
They are quite a delicate little fish and won’t appreciate being kept with larger, more boisterous species, especially if they have a tendency to nip fins. Good water quality is vital.

Neon dwarf rainbow, Melanotaenia praecox

This small, iridescent rainbow from Irian Jaya in Indonesia reaches about 5cm/2″, with females being a little smaller. It’s a lovely fish and looks great in a group of six or more in a tank planted heavily with fine-leaved plants such as Cabomba and Water wisteria.
It will often spawn in the tank if you get the water right (clean, slightly alkaline water is preferable), but other fish in the aquarium will usually polish off the young.

Boesemani rainbow, Melanotaenia boesemani

If your tank is 90cm/36″ or more in length, a group of four or five Boesemani rainbows will make the tank look very showy. These rainbows reach about 10cm/4″ on average and take a couple of years to really develop. The adults are truly stunning and usually sell out quickly, so you’ll normally only see drab-looking youngsters on sale.
Kept in a group consisting of a few females and a couple of males in a planted tank with slightly alkaline water, these fish should start to colour up nicely after a year or so, especially if you give them a special colour-enhancing food.

Red rainbow, Glossolepis incisus

The Red rainbow is another one which takes longer to develop. Females and young fish are bronze in colour, but adult males turn solid red and often have a prominent yellow stripe along the top of their head when they mature. At up to about 15cm/6″, these are fairly large fish so a tank of 120cm/4′ is sensible if you want to keep a small shoal happy. Don’t pick out all of the colourful specimens when you buy them. If you want them to look really good, it’s important to give the males plenty of females to show off to. Feed them a colour-enhancing food to bring out the red and don’t raise the temperature too high as they have a tendency to look washed out.


There are hundreds of different species of characins (pronounced kah-ra-sin), but the most common are the tetras. These small, usually shoaling fishes, are often great community fish – although one or two of them can be a little nippy, so check with your dealer first.

Neon tetra, Paracheirodon innesi

The world’s most popular tropical aquarium fish is cheap (about a quid), widely available and peaceful. It looks best, and is happiest, when kept in a big group, so spend a little more and buy a dozen or more if you have the space.

Cardinal tetra, Paracheirodon axelrodi

The classier Cardinal tetra is a bit more expensive than the Neon but it’s arguably a bit better looking. These are available either as wild-caught or captive-bred fish. We think the captive-bred ones from the Czech Republic are the most reliable quality and adapt well to harder water than wild fish.

Black Neon tetra, Hyphessobrycon herbertaxelrodi

The Black Neon tetra can get a little larger than the Cardinal or Neon and looks best when kept in a well-planted tank with a dark substrate and slightly subdued lighting.


Unfortunately, many barbs have an undeserved reputation for being a little nippy, but actually only a handful of them nip the finnage of fish and then it’s only easy targets, like guppies, that suffer.

Tiger barbs, Puntius tetrazona

Tiger barbs are one of the barbs that you do need to watch out for as they may nip fins if they are kept in small groups, or individually. They are happiest in a shoal, so get six or more, and don’t mix them with any fish that have long flowing fins – just to be safe. They leave other short-finned fish well alone providing they are kept in a shoal. Don’t forget that the Tiger barbs on sale in the shop are really very, very young, and have lots of growing to do. Adult ones are very deep and stocky and commonly reach 8cm/3″ when conditions are right. A tank of 60cm/24″ is really the minimum if you want to keep a small group properly.

Ruby barbs, Puntius nigrofasciatus

Although they can look a little like Tiger barbs when small, Ruby barbs change dramatically as they mature. Some of them can be a vibrant mix of black and red and they are lovely to look at in a group against a backdrop of bushy plants. They are lively but less boisterous than Tiger barbs and rarely nip fins. Keep a mixture of males and females and give them a colour food to get them to colour up.

Denison’s barb, Puntius denisonii

Denison’s barb, also called the Red torpedo, has only been readily available for a few years. However, in this short time it has made an enormous impact on the hobby. Unfortunately, since it’s still comparatively new to the UK trade it also comes with a high price, but this is likely to drop as fish farmers turn their attentions to producing it on a commercial scale.
It reaches 10-15cm/4-6″ and can be safely kept in a small group in a planted community tank of about 90cm/36″ or more. Expect to pay £10-20 per fish at the moment

Larger barbs

Unless you have an enormous tank (well over 120cm/4′), there are some barbs that are best avoided. Red fin cigar sharks, Leptobarbus hoeveni, are the biggest you are likely to see and can reach 45cm/18″ in aquariums. Tinfoil barbs, such as Barbonymus schwanenfeldi, also get very large at about 30cm/12″ on average. Unfortunately, you’re quite likely to see both of these for sale in the average pet shop as a community fish. Avoid them unless you are setting up a very large tank for them.

Silver shark, Balantiocheilos melanopterus

The Silver, or Bala, shark although not strictly speaking a barb is a close relative. These fish are often seen for sale at small sizes but have the potential to hit 20-25cm/8-10″.
They are peaceful, active shoaling fish but can be a little jumpy, so they should only be kept in tanks that are at least 120cm/4′ long. Avoid sharp decor in the tank as they have a tendency to bump into things


Cichlids (pronounced sick-lids) are something of a special case, and many really need to be kept in a species tank all on their own.

Angelfish, Pterophyllum scalare
Angels don’t always live up to their name. They are cichlids, after all, and these fish in general do have a reputation for being a little feisty. They’ll usually mix quite well with most community fish, but you do need to make sure there are no tiny fish present – adult Angels can swallow Neon tetras whole. It’s also wise to avoid any fish that are prone to fin-nipping, and also other cichlids that might squabble over the same sort of territories.

The other thing to look out for is the size of the tank. Adult angels are quite large and very tall, so as a minimum you’ll need a tank of 90 x 30 x 45cm/36″ x 12″ x 18″.

Angels only shoal outside the breeding season and can become aggressive when they pair off.
Try and start with about four youngsters and see if you get a pair. Most dealers will happily swap any adults you have, providing you OK it with them when you buy the fish.

Rams, Mikrogeophagus ramirezi

Unless you have soft, acidic water, it’s probably best that you avoid Rams altogether. They aren’t easy for the newcomer to keep at the best of times, and unfortunately, many of those on sale are of dubious quality.
Since males are the most colourful and saleable, Far Eastern suppliers sometimes expose fish to hormones to produce batches of male fish. Unfortunately, these are useless for breeding.

If you’re looking for good-quality fish, seek out some tank-bred ones from the Czech Republic or Germany. These are usually stockier and more colourful than the Singapore fish and well worth paying extra for. Alternatively, look for the Bolivian ram, M. altispinosa, which are a bit tougher.

Kribensis, Pelvicachromis pulcher

Kribs are an ideal first cichlid and can be kept, usually quite safely, in a community aquarium. However, when they spawn they will become quite territorial and will aggressively defend their territory, so you must be careful what you mix them with.

Most shops should be able to find you a sexed pair (a male and a female). Give these a shelter, such as a piece of bogwood or an old clay flowerpot, and they may reward you with a brood of young.
The parents will guard and herd these around the tank, which makes them fascinating fish to keep.

This article was first published in the December 2004 issue of Practical Fishkeeping magazine.

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