Fancy and long-finned fish: the extra care their body shape needs

Quick answer

Long fins are heavy, and a fish that has to work to swim has less in reserve for everything else.

Fancy goldfish, show bettas, fancy guppies and the long-finned forms of ordinary species are not sick. They are shaped differently, and that shape changes the tank, the food, the tank mates and what counts as normal.

The traits people buy them for are trade-offs. Trailing fins cost swimming efficiency. An egg-shaped body compresses the gut and the swim bladder. A hood grows over the eyes. Protruding eyes sit outside the protection of the skull. None of this is a disease, but each of them raises the cost of an ordinary mistake.

• Never cut a fish's fins or a goldfish's hood at home. Both are living, vascular tissue.
• Reduce current, not surface movement. Long-finned fish exhaust themselves in flow, but they still need gas exchange at the surface.
• Short-bodied fancy goldfish need sinking, pre-soaked food fed at depth, because gulping air at the surface is where most of their buoyancy trouble starts.
• Never keep fancy goldfish with single-tailed goldfish. The single-tails eat first, swim faster and will strip the food before a fancy reaches it.
• Anything sharp, anything with a strong intake slot and any plastic plant is a torn fin or a damaged eye waiting to happen.

Decide in 60 seconds

Why shape changes the care

Selective breeding for appearance in ornamental fish works the same way it does in dogs. Fixing an exaggerated trait means fixing whatever else it drags along.

Long finnage adds drag without adding power.

A veiltail goldfish or a rosetail betta carries a much larger surface area behind it than the fish it was bred from, with the same muscle. Every movement costs more. In practice this shows up as a fish that tires in current, arrives late to food, cannot escape a harasser, and rests on the substrate or on a leaf far more than a wild-type fish would.

Long fins also present far more surface for damage. Torn fin tissue is an open wound, and an open wound in water with elevated organic load is where opportunistic bacterial infections start.

A shortened body compresses everything inside it.

The round, egg-shaped fancy goldfish body is a vertebral column that has been shortened without shortening the organs. The intestine folds into a smaller space, and the swim bladder, which is a two-chambered gas organ used for fine buoyancy control, sits distorted.

Add food that swells, or air swallowed at the surface, and a system with no spare room becomes unstable. This is why buoyancy problems cluster so heavily in these varieties and are rare in a common goldfish in the same tank.

A wen keeps growing.

The hood on an oranda, ranchu or lionhead is proliferated epidermal tissue. It does not stop at an attractive size. In older fish it grows over the eyes, restricting vision, and over the nostrils, which matters because goldfish find food partly by smell.

The folds also trap detritus. Water quality that a smooth-headed fish tolerates produces reddening, ulceration and infection between the folds of a large wen.

Protruding eyes lose their protection.

A telescope eye sits on a stalk of tissue outside the line of the skull, and a bubble eye carries a fluid-filled sac in front of it. Both are hit by things a normal fish's eye would never contact: rock edges, plastic plant leaves, a net, a filter intake, or the mouth of an inquisitive tank mate.

Vision in these varieties is poor as well as vulnerable, which changes how they find food and how they interact with faster fish.

Losing the dorsal fin loses stability.

Ranchu, lionhead and celestial varieties have no dorsal fin. The dorsal is the keel that keeps a fish upright against roll. Without it, a current that another goldfish ignores tips the fish over and it has to work continuously to stay level.

Telling a trait from a disease

Learn what your particular fish looks like when it is well, from the side, in good light. Almost every judgement below is a comparison with that baseline.

This is where owners of fancy varieties go wrong in both directions, treating normal conformation as disease and dismissing real disease as "just how it looks".

The two comparisons that catch the most real disease early are the scales-standing-out test for dropsy, best done by looking down on the fish from above, and the fin margin test, which is simply whether the outer edge of the fin looks like fin or looks like something else.

The tank that suits a compromised body

Reduce current, keep surface movement.

These are different things and conflating them causes fish to suffocate. Long-finned and dorsal-less fish need low water movement where they swim, and they still need the surface broken so oxygen can enter and carbon dioxide can leave. Use a spray bar aimed along the back glass or at the surface, a filter baffle, or a wider outlet, rather than simply turning the filter down.

Remove everything sharp.

Rock with edges, resin ornaments with thin projections, driftwood with splinters and above all plastic plants. Plastic plant leaves have hard edges and moulded seams that shred fins and scratch protruding eyes. Silk plants and live plants do not.

Guard the intakes.

A sponge prefilter over the intake strainer stops a long fin or a bubble-eye sac being drawn into a slot. This single change prevents a large share of the injuries in this group.

Choose the substrate for the mouth as well as the fins.

Fancy goldfish root in the substrate and pick up gravel, and a short-bodied fish that swallows a gravel piece has less room to move it along. Smooth sand, or stones too large to fit in the mouth, are the two safe options.

Choose tank mates honestly.

Avoid known fin nippers. Avoid fast, greedy species that will clear the food before a slow fish arrives. Never mix fancy goldfish with common or comet goldfish, which are faster, longer bodied, and will outcompete them at every meal.

Be careful with suckermouth catfish kept with slow-moving, high-bodied fish. Some will rasp at the flanks of a slow fish, damaging the mucus layer and opening the skin to infection.

Hold the water to a higher standard than usual.

A compromised fish has less reserve. The nitrate load and the organic build-up that a robust fish shrugs off will degrade fins, inflame a wen and slow healing in a fancy variety. Bigger and more frequent water changes are the correct response to fin damage far more often than medication is.

For bettas specifically.

Depth, flow and heavy finnage combine badly. A betta must reach the surface to breathe air through its labyrinth organ, and a heavily finned fish in a deep tank with a strong current can genuinely exhaust itself doing so. Keep the flow low, and provide broad leaves or a resting hammock near the surface. Those are functional equipment, not decoration.

Feeding a short-bodied fish

Buoyancy trouble in fancy goldfish is mostly a feeding problem wearing a medical costume.

Stop feeding floating food. A fish that feeds at the surface gulps air with every mouthful, and swallowed air in a compressed body cavity is the most common cause of post-meal floating.

Pre-soak pellets. Dry extruded pellets swell after they are eaten. Soaking them in tank water until they are fully expanded before feeding removes that expansion from inside the fish.

Feed at depth. Sinking food, delivered below the surface, keeps the mouth away from the air.

Feed smaller amounts more often. A single large meal distends a gut that has nowhere to expand into.

Include vegetable matter. Blanched deshelled peas, blanched courgette and similar foods are commonly used to move a sluggish gut, and many keepers use a regular vegetable day for buoyancy-prone fish.

Watch the temperature. Goldfish digestion slows as the water cools. In an unheated tank in winter, the same meal sits in the gut for longer, and short-bodied varieties become more prone to buoyancy problems in exactly that period.

If buoyancy problems persist between meals, worsen over weeks, or come with loss of appetite, clamped fins or a change in droppings, the problem has stopped being dietary and needs proper investigation.

Handling and day-to-day care

Do not net a long-finned fish. Netting tears fins on the mesh, and lifting a fish in air makes its own weight pull against the fin rays. Use a rigid container: guide the fish into a jug or specimen box under water and lift the container with the fish still in water.

Do not chase. A stressed, exhausted long-finned fish is more likely to crash into decor, which is how eyes get damaged.

Check the fins weekly. Look at the outer edges specifically, not the general shape. Photograph them from the side, from the same distance, so you can compare.

Check the wen monthly. Look for redness where the folds meet, a change in texture, and whether it is starting to encroach on the eyes or the nostrils.

Check the eyes weekly in telescope and bubble-eye varieties, for cloudiness, scratches, or a sac that has changed size or shape.

Watch feeding, not just the fish. The most useful thirty seconds you will spend is watching a feed and seeing whether your fancy fish actually gets any.

Choosing the next fish

The severity of the trait is the severity of the care.

A moderate fantail with a body it can move and eyes that sit in the head lives a considerably easier life than a rosetail betta with fins so heavy the fish rests constantly, or a ranchu with a wen already over its eyes.

At the point of purchase, look at whether the fish can swim horizontally without effort, whether it holds itself level, whether the eyes are clear and unobstructed, and whether it competes for food in the shop tank. A fish that is already struggling in a shop tank will not improve in a home tank.

There is nothing wrong with choosing the less extreme version. It is the same decision a sensible buyer makes when choosing a dog with a muzzle.

The routine that keeps a fancy fish sound

What never to do

Do not trim fins. They are living tissue, cutting them hurts and bleeds, and torn fins regrow well when the water is right and the cause is removed.

Do not trim or pick at a wen. It bleeds heavily and the folds become infected easily.

Do not use plastic plants or sharp ornaments with any long-finned or protruding-eyed fish.

Do not house fancy goldfish with single-tailed goldfish, or with fast, greedy or nipping species.

Do not feed floating flake or dry unsoaked pellets to a short-bodied goldfish.

Do not net a long-finned fish or lift it in air. Move it in water in a container.

Do not reach for medication first when fins look ragged. Test the water, find the physical cause, and improve conditions. Most fin damage in these varieties is mechanical or water quality driven, and medicating a healthy filter causes a second problem.

Do not assume a fish that rests a lot is lazy. In this group it is often a fish that cannot afford to swim.

When to get help

Seek advice from an aquatic vet or an experienced fish keeper promptly for fin margins that are receding, discoloured or fuzzy, for an eye that has become cloudy, injured or is bulging on one side only, for a ruptured bubble-eye sac, and for redness or ulceration in a wen.

Act urgently for a fish that cannot right itself, cannot reach the surface, or has stopped eating, and for any fish whose scales are standing out from the body.

Before you ask for help, gather the information that actually answers the question: your test results for ammonia, nitrite, nitrate and pH with the age of the test kit, the tank volume, how long it has been running, the filter and flow arrangement, the full tank mate list, what and how often you feed, what changed recently, and a clear side-on photograph of the whole fish plus a close-up of the affected area.

For fancy varieties, add one more line that people always forget: the exact variety. A ranchu, a bubble eye and a comet with the same symptom can each need a different answer, and the shape of the fish is part of the diagnosis.