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metabolic dietary

Bloat and constipation (digestive)

Mild-to-moderate abdominal swelling without raised scales, often linked to overfeeding, a diet too low in fiber, or dry food that expands after eating. Very common in bettas, goldfish, and other heavy eaters. Distinguished from dropsy by the absence of pinecone scales and by a more localized, often asymmetric swelling.

Monitorpattern match not diagnosis1 source note

Do first

  • Fast the fish for 2–3 days. This is both diagnostic and therapeutic.
  • Check and correct water temperature. Ensure it is within the species' optimal range.
  • After fasting, offer a single de-shelled cooked pea (for omnivores and herbivores only).
  • Switch to a higher-quality, lower-filler diet. Avoid foods with high starch or corn meal as a primary ingredient.
  • Reduce portion sizes going forward. Most fish should eat what. They can consume in 2–3 minutes, once or twice daily.

Escalate if

  • Bloating persists for more than 7 days despite fasting.
  • Scales begin to raise reclassify as potential dropsy.
  • Fish completely stops eating and becomes severely lethargic.
  • Swelling is hard and uneven rather than uniformly round possible internal mass or cyst.

Water clues

These readings can push this pattern higher or lower in the triage result.

temp below species min+3

Cold water slows digestion dramatically and commonly causes constipation. Check temperature.

Care protocol

Follow only the steps that fit your species, tank inhabitants, and medication label.

Distinguishing bloat from dropsy

  1. Dropsy: scales raised outward (visible from above as a 'pinecone'), often bilateral eye bulge, severe lethargy.
  2. Constipation/bloat: rounded belly but scales lie flat, fish is still reasonably active, no eye changes.
  3. View the fish from above if scales are raised, this is not simple constipation.
  4. Betta bloat in particular can appear alarming but often resolves with fasting.
Cautions
  • Do not treat with antibiotics for simple constipation. It will not help and damages the microbiome.
  • If scales are even slightly raised, treat as a potential dropsy case. The two can overlap.

Dietary correction

  1. 2–3 day fast, then offer a piece of cooked, de-shelled frozen pea (green peas are a laxative for most freshwater fish).
  2. Do not use peas for obligate carnivores (bettas, discus, large cichlids) offer a small amount of live or frozen food instead.
  3. After resolution, switch to a diet with more variety and less dry food expansion potential.
  4. Soak dry pellets in water for 30 seconds before feeding. This reduces how much they expand post-ingestion.
  5. Feed smaller amounts more frequently rather than one large daily meal.
Cautions
  • Peas are safe for most herbivorous and omnivorous freshwater fish but inappropriate for carnivores.
  • If bloating does not resolve within 5–7 days of dietary correction and fasting, investigate further.

Source notes

References and context notes used for this triage entry.

Nutritional diseases in ornamental fish general referenceUF/IFAS extension refer to species-specific nutrition guides.
Run Symptom CheckerCompare this pattern against water readings, affected count, and recent tank context.Ask AdvisorUse TankFlare Advisor to review this against your saved tank and recent logs.

Related patterns

Similar symptoms or risk factors worth comparing before treatment.

Medium prioritySwim bladder disorder

Loss of buoyancy control fish floats at the surface, sinks to the bottom, swims sideways, or struggles to maintain position. Can be caused by bacterial infection, constipation/overfeeding, physical injury, genetic defect (common in fancy goldfish), or internal parasites.

High priorityIntestinal prolapse (rectal prolapse)

A section of intestine protruding from the vent, appearing as a pink, red, or brownish tube-like structure. Often confused with Camallanus worms, but prolapsed tissue is wider, irregular, and does not move independently. Usually caused by severe constipation, straining, internal parasites, or bacterial infection of the gut.

UrgentSpring viremia of carp (SVC / Rhabdovirus carpio)

A notifiable viral hemorrhagic disease affecting cyprinids (koi, goldfish, carp) primarily in spring at water temperatures of 11–17°C (52–63°F). Causes hemorrhaging, abdominal swelling, protruding eyes, and mass mortality. SVC is a regulated disease in many countries suspected outbreaks must be reported to animal health authorities.

MonitorOverfeeding and obesity

A fish that is visibly overweight rounded or bulging abdomen that has developed over weeks or months due to consistently feeding too much. Unlike dropsy or bloat from constipation, this is a chronic condition. Common in bettas, goldfish, and cichlids. Fat deposits around organs can cause liver disease, buoyancy problems, and shortened lifespan.