Aquarium fish hiding is usually not a cause for alarm as it is normal for some species. But it can be scary if it starts happening suddenly and coupled with other odd behaviors like a fish not eating or looking lethergic.
In such instances, it’s not unusual for fish keepers to assume their fish are dying. Most even query whether that is the first sign of their pets imminent demise.
Sadly, it could be, but in rare occasions.
Most times, aquarium fish will hide when they are stressed either by external factors or internal (health) issues, though some species are just skittish or shy and will hide whether they are stressed or not.
External stressors that could make your fish hide include aggression from other members in your community, water conditions and quality particularly for new fish and the general environment like lighting more so with plecos, cories, and loaches.
Internal or health factors include parasites, ailments, and digestive issues.
To find out more about fish behavior, especially hiding tendencies, please read on.
What Does It Mean When Your Fish Hides?
Your fish could be hiding because of many varying reasons. As I mentioned above, it’s mainly because of some external factors or internal reason within their system.
But to be sure, you would need to investigate a little more. Look for other odd behaviors, and also check the conditions in your fish tank including ammonia and nitrite level, ph, and temperature.
Some tell-tale signs that you should be looking for include the fish’s feeding habits, general health and well-being (breathing and movement), and the relationship between members of the community.
Below are a few combinations of a fishes behavior that are a little more direct and easier to decipher.
#1 — Fish Hiding and Not Eating
A community aquarium is a wild place where any sign of weakness will welcome attacks on the weaker members by stronger fishes. This behavior is especially imminent during meal times, where strength and positions in caste are well manifested.
As such, the lowest members of the group may hide and not eat while trying to protect themselves from attacks.
If that’s the case, the first thing you will want to do is to find out which fish is the deranged oddball in your tank that’s keeping others from coming out of hiding to feed.
However, a fish that would otherwise feed with others can also suddenly stop if their strength is compromised.
So, if only one fish is hiding, most likely the behavior has to do with an ailment or infection that’s making the fish feel intimidated and vulnerable to attack. Such individuals will also exhibit other signs like general weakness (lethargy), slow movement and swimming, heavy breathing, and incase of parasitic infection on the skin, scratching on surfaces like rocks, wood, decor, and plants.
As a precautionary measure, find out if your fish has a problem with its digestion as well. Be sure to consider all possibilities including issues like swim bladder disease, which are closely related to a fishes metabolism.
That said, it is also important you note that some fishes like kuhli loach are nocturnal and will stay in hiding all day and only come out at night to feed. Thus, research your fish’s behavior, in case you haven’t done this already.
#2 — Fish Hiding and Breathing Fast (Heavy)
The first thing I would do if I had a fish breathing heavy and hiding, is to test my water, and so should you. Because eight out of ten times, things that affect a fish’s breathing has to do with the environment and especially the water quality or conditions.
Check for ammonia and nitrites levels, temperature, and ph. Nitrates are not too harmful, but you may also want to make sure they are at a safe level.
The other thing I would consider is ailments and parasites.
How does water quality and diseases affect your fish respiratory system?
These problems stimulate the gills to secrete mucus as a protective measure. However, the slime covers the gills and limits the water-gill contact necessary for gas exchange and off-loading toxins like ammonia.
Therefore the fish has to increase it’s respiration rate to off-set this reduced efficiency, which is what we consider fast or heavy breathing.
Given this background, it is also true a fish would breathe fast when there is insufficient oxygen in the tank. The best solution in such instance is to add an air pump in your fish tank.
That said, fish have adapted to living in environments full of threats and can conceal these signs pretty well. It is good practice to know the natural respiration rate of your fish, so that when things are abnormal, you will be able to spot it. Respiration rates of fish can vary widely ranging anywhere from 20 to 80 opercular movements per minute under normal conditions.
#3 — It is Normal For New Fish to Hide!
Yes, hiding is a pretty natural behavior of most fish when introduced to a new environment such a fish tank, especially if there is an existing community.
Most times the fish will hide as they try to acclimate to the water column’s ph, temperature, and what have you. Once they are properly accustomed, they will most likely venture out and explore.
In other instances, they just don’t want to be too overbearing and venture into other fishes’ territories. This especially true for species that establish a pecking order or territorial fish like betta and cichlids. With time, the new member will identify an unclaimed turf and own it, then he will start swimming more freely, and confidently.
Sometimes when it’s not either of the two reasons above, it might be your fish came in battling an infection, that’s why you must quarantine new member for two (2) to four (4) weeks before introducing them into the main aquarium.
If after trying all the above solution but your fish is still hiding, try tweaking the water parameters because maybe the fish is used to a different settings.
From my experience, some fish prefer a lower ph than others, while others prefer some amount of salt in the water even though they are freshwater species. Of course, tropical fish require a heated tank with the temperature anywhere from 72° F.
#4 — Why Your Fish are Hiding All of a Sudden
Sometimes, a fish that would usually not hide might start spending most of its time behind plants and decor.
Such behavior is mostly triggered by a change in the environment such as water quality, temperature, chemical imbalances, and ph setting. Once the tank stabilizes, your fish will most likely get back to their usual self and venture out more.
That said if only one fish is hiding, a change in the environment might not be the reason. More likely, your fish is battling an infection, or there is a bully in the tank.
I would therefore recommend you observe the individual over the next couple of days, see if you notice any other odd behaviors like reduced appetite, lethargy, and heavy breathing.
If the fish exhibit any of the other signs, it is probably sick, so take it out and place in your hospital aquarium for specialized care.
Do Fish Hide When They Are Dying
Aquarium fish do not exactly hide because they are dying, but they do hide when they are sick, which could quite easily lead to death, more so if you don’t find them in time.
Obiously, dead fish don’t swim, so if your fish goes into hiding while sick and die under the cover, the time you saw it last may just be the final moment you ever see it. What’s even worse is if you have other fishes in the tank that don’t have a problem eating dead tankmates, you might not get a body.
For that reason, it is well-advised to keep a keen eye on your fish at all times and try to identify any individuals acting out of character before they become too weak and retreat into hiding.
Normally, a sick fish that is quite close to death will be lethargic, struggling to swim and breathing heavy. If the issue has to do with parasites or infections that affect the fish parts like gills and fins, you may see lacerations on affected organs.
Some infections like swim bladder disease, dropsy or whirling disease may affect your fish to an extent even the swimming changes. Commonly, affected individuals swim erratically.
On other times a sick will not hide, but instead, will hang around the bottom of the tank or on the surface, not swimming too far. Some will even hang out around your equipment such as heaters or decor like driftwood.
In conclusion, as you may have realized, aquarium fish can hide for many different reasons, so I cannot emphasize enough how important it is to observe your fish keenly and at all times. This will make it easy for you to figure out what’s wrong with your fish in case they start showing odd behavior like hiding or not eating.
Happy Fish Keeping