Goldfish Sitting at the Bottom of the Tank? (8 Reasons)

Healthy goldfish are active swimmers. They move around their tank all day, exploring its corners, interacting with other fish and plants, displacing substrates in search of food, and eagerly rising to the surface during meal times. These active fish will rarely remain immobile or in one place for long periods. They should continue to swim even as they eliminate their waste. The only time they’ll seem to rest, likely along the bottom of a tank, is when they are asleep. 

Any diurnal changes to a goldfish’s behavior may indicate a number of internal and external stress-related issues. It can also hint at the presence of parasites, genetic abnormalities, or metabolic disorders. If you find that your goldfish has been resting on the bottom of its tank for a prolonged duration, it would be necessary to first check the water’s parameters.

Goldfish may continue to appear lethargic or immobile even in optimal water conditions or after all possible environmental stressors have been removed. This could mean that the problem is internal rather than external. Immobility may be accompanied by other symptoms like loss of color and lack of appetite. Some of the most common culprits behind goldfish inactivity are listed below.

1) Poor water quality

Like the air we breathe, water is crucial to a goldfish’s capacity to survive and recover from stressors. Imbalanced or excess components of their fluid environment can cause toxic symptoms. Both the water chemistry (i.e., dissolved nutrient concentrations, oxygen availability, pH levels) and physical parameters need to be within their preferred range.

Water quality is affected by how often water changes are performed, the efficiency with which it is filtered, or the presence of excess nutrients and potentially harmful microbes. If ammonia and nitrite concentrations, both of which need to be kept at 0 – 0.05 ppm at most, are elevated, your goldfish’s ability to breathe may be affected. Toxic nutrient levels can cause it to grow lethargic, causing it to swim awkwardly or remain at the bottom of the tank.

When pH levels are slightly acidic or basic, a goldfish may begin to display sluggishness. Similar behavior may be manifested due to poor oxygen availability and excessively cool or hot water temperatures. Make sure to regularly test your tank’s water and conduct regular water changes to maintain optimal conditions.

2) Swim bladder issues

A goldfish’s swim bladder is responsible for controlling its capacity to remain buoyant in water. This organ is either filled with gas or deflated depending on the fish’s desired position in the water column. Thus, any abnormalities affecting its functions can cause your goldfish to swim on its side or remain upside down. These may also prevent it from either rising to the surface of the tank or sinking to the bottom.

Swim bladder disease can be caused by genetic issues, the presence of parasites, metabolic issues, egg impaction, and more. Once it worsens, this disorder can perpetually prevent your fish from remaining neutrally buoyant – even in optimal water conditions. It may survive for some time – bobbing up and down or remaining immobile on the bottom of the tank instead of swimming in one desired direction – if it is provided with sinking food. While this disorder may be treated in its early stages, it can cause permanent damage and even lead to death.

3) Parasites

Immobility may be a sign of internal complications due to parasitic infections. Goldfish parasites may be found on the surface of their face, fins, and scales. These include fish lice, fish leeches, and gill maggots. They may also slowly spread to damage internal organs, such as the swim bladder and digestive system. As these parasites grow, they may cause open wounds, ulcers, and fungal or bacterial infections. All of these may eventually lead to lethargy, poor breathing, compromised swimming abilities, and even death.

If you suspect that your immobile goldfish has been plagued by parasites, it would be wise to isolate it in a separate tank and provide it with anti-parasitic medication. Some visible types of parasites may be removed manually, but note that this task would be best left to an expert. If more than one fish shares the same symptoms, it may be necessary to treat the entire tank.

4) Underlying diseases

Many internal diseases go undetected until they are manifested by progressively worse symptoms. Those that are associated with the gastrointestinal tract, potentially leading to constipation, can severely impede your goldfish’s ability to swim. Constipation can affect the swim bladder’s capacity to inflate, preventing the fish from changing its position in the water column. This may also cause them to look swollen and to swim upside down.

Another disease that may have similar symptoms is dropsy. Typically caused by bacterial buildup, this disease can prevent your goldfish from releasing excess fluids as a form of osmoregulation. Often triggered by stress, this may result in an inflated appearance, scales that jut outward, bulging eyes, and fin discoloration. In its swollen state, the fish may be unable to rise to the surface or swim. While this disease may be treated with antibiotics in its early stages, it is unfortunately often fatal.

5) Morphology-related issues

Some fancy goldfish varieties have been bred with the intention of accentuating certain morphological features. These tend to come at the cost of some important bodily functions and swimming abilities. Round-bodied fancy goldfish breeds – ryukins, bubble-eyes, orandas, and more – are especially vulnerable to buoyancy-related disorders. They may struggle to swim up and down in the water column, let alone see what’s directly in front of them.

Ornamental breeds with relatively large fins may also be more prone to remaining close to or on the bottom of their tank. Their fins may gradually grow too heavy for them to actively carry. As these are also more likely to touch the substrate, they may eventually become damaged by pathogens.

6) Overcrowding

One of the worst things you can do to a school of goldfish is place them in a tank that’s too small. Stocking a conservative density of fish, especially in an enclosed and controlled water system, is crucial for their normal growth performance and well-being.

Overcrowding quickly leads to water quality problems like low dissolved oxygen, excess ammonia, and competition for food. These can quickly affect fish with weaker immune systems, causing them to show symptoms of stress, hide, or remain immobile.

A goldfish resting on the bottom of a tank is an unsurprising result of overcrowding. Though these fish are often overstocked in pet stores, largely due to their peaceful nature and their attractive appearance in groups, simply increasing filtration rates may not make up for the lack of space in the long-term. Experienced hobbyists know that goldfish require relatively large tanks to grow, thrive, and live out their full lifespans. They may argue that placing a goldfish in a small fishbowl or stocking too many – even in an adequately-sized tank – is tantamount to animal cruelty.

7) Cool temperatures

Water temperature affects the metabolic rates of cold-blooded fish. Goldfish should ideally be kept in tanks with a water temperature maintained at 68 – 74˚F (20 – 23˚C). At this range, they can comfortably metabolize their food and are unlikely to experience heat or cold stress. Healthy specimens can tolerate temperatures that slightly dip below this range. Once temperatures hit 59˚F (15˚C) and below, they may struggle to digest their food or they may not eat at all.

Unable to undergo efficient metabolism, trapped food can result in constipation or impaction injuries. These may affect a goldfish’s capacity to control its swim bladder, preventing it from swimming in a normal manner. In outdoor ponds, goldfish may naturally be observed to remain at the bottom, where temperatures are more likely to be higher, all throughout winter. In regions with harsh winters, it is recommended that they be brought indoors and kept in a heat-regulated tank.

8) Acclimatization-related stress

When fish are newly introduced into a tank, they may take some time to grow acclimated to its conditions. Subtle differences between the temperature, nutrient concentrations, light exposure, pH level, and overall shape of their new and old enclosures can cause them to grow disoriented and stressed. When goldfish are not gradually introduced into a new system, they may go into shock.

Improper acclimatization weakens a fish’s immunity and triggers its flight response. It may cause it to hide, lose its appetite, attempt to escape, and become lethargic at the bottom of the tank. Prior to releasing your fish into a new tank, allow it to gradually become acclimatized to the water’s conditions. This can be done by allowing its oxygenated bag of water to float in the tank for several minutes.

Introducing new goldfish into a previously-stocked tank of goldfish can also cause the initial population of fish to become stressed. A new specimen can lower oxygen rates in poorly-filtered tanks. It may also bring parasites and diseases. If you’re concerned about how your older ornamentals may respond to a new fish, a quarantine tank would be a recommended part of the acclimatization process.