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9 Common Mistakes of Freshwater Fish Owners

By Edited Apr 20, 2015 5 7

Fish in a Bowl

Keeping fish in an aquarium is a truly relaxing hobby. However, beginners may feel overwhelmed by the number of unfamiliar aquarium equipment available for their care. I was also one of those who felt daunted when I first started this hobby. Not to mention this hobby started not out of my own decision, but as a result of someone sending off his pet fish to me (for personal reasons). Thankfully, I didn't have to go through much trial and error as I was already given clear instructions by the original owner.

Gradually, I learned to appreciate this hobby. Despite not being able to hug or pet my scaly friends, feeding and watching them swim around are as equally rewarding. 

When you get a new fish, placing him in a bowl and feeding him regularly is not enough. Without giving the appropriate care, he may become stressed and unhealthy, just as what had happened to my pet when I was six years old. I had always thought that fish are very fragile creatures because I kept losing my pets one after the other.

When I happened to pick up with this hobby many years later, besides getting mentored by a more experienced fish owner, I also started reading a lot about this topic. I learned to pinpoint my own mistakes back then. 

I decided to write this article to help beginners avoid the mistakes commonly encountered by new fish owners. I write out of my six years of becoming an aquarist. Just to give you reference, my own experience lie mainly on caring for cichlids, thus, this article is directed particularly to freshwater tank owners.

Note: Just to clear up some confusions, as you read this article, you will notice that I will refer to the fish as him or her as I dislike using the pronoun it to refer to animals.

Mistake #1: Not Using a Bucket Exclusive for Fish Keeping

I committed this same mistake when I was still a beginner. I had used the bucket for the laundry for transporting water into my tank (fortunately, I learned about this mistake early enough to prevent further harm). Detergents are hard to eliminate from containers and so using the same container for the tank may transfer harmful chemicals to the fish. Use the equipment and storage exclusively for the fish. Your fish will surely thank you for that.

Mistake #2: Using Water Directly from the Faucet

Credit: Gabriel Rocha | Flickr
Two things may happen if you use water directly from the tap. One, you are introducing toxic chemicals into the tank. Such chemicals may be in the form of chlorine and/or chloramine that are used to treat the water. Other chemicals may come from the impurities acquired from the water pipes, such as copper. Two, by using water directly from the faucet, there is a great chance that certain variables (such as temperature, pH, and hardness) will differ greatly from the tank water conditions. Once added into the tank, fluctuations may occur in such a way that will not be tolerated by the fish.[1]
To solve this problem, store the tap water in a bucket and treat it with water conditioner. A good water conditioner neutralizes pH and hardness and also eliminates chlorine and chloramine. Once conditioned, allow the water to sit for several hours near your aquarium to allow the bucket water temperature to be as close as the tank water temperature. 

Mistake #3: Overfeeding the Fish

One of the most common mistakes of fish keeping is overfeeding them. Fish appears to be constantly hungry, and many fish owners love watching them eat. My fish seem to go crazy for food like they haven't been eaten for months, when in fact I had just fed them the day before. In truth, fish can survive not eating for at least a week or more (of course, I wouldn't have the heart to starve them that often unless when I had to go away for that long). Feeding them once or twice a day is enough.

The amount of food varies, but the rule of thumb is: feed them for as much as they can consume within four to five minutes.[2] I notice that my cichlids' tank get cloudy (one sign of overfeeding) easily when I feed them twice a day. I had switched to feeding them once daily due to that reason. In addition, I also skip a day or two per week of feeding to prevent their stomach from reaching their limit. When it comes to feeding, it is always better to underfeed than to overfeed them.

Mistake #4: Overcrowding the Fish

Overcrowded Tank
Credit: Sally Butcher | Flickr

Fish become aggressive when crowded in a small space.

It may be fun to watch several fish living together in a single tank community. After all, it will be too bad to see your pet go lonely. However, some fish, such as the siamese fighting fish and flowerhorn, are highly aggressive. They can become very hostile to other fish and so keeping them alone in the tank may be the better option. Even social fish will also tend to become aggressive toward each other when overcrowded as they compete for territory and food.[3] In addition, keeping several fish in a tank give off a lot of waste - waste that are too much for the them to tolerate. 

If you do decide to add new fish to your tank, make sure that your tank size is large enough to accommodate them. Adding new fish should be done gradually.

Mistake #5: Putting in Harmful Objects Inside the Tank

Credit: John Fowler | Flickr

Avoid placing wild-caught items inside your aquarium.

Decorating a tank is part of the fun of fish keeping. They provide good hiding places for fish and make the tank look less boring. However, you should practice caution when it comes to choosing your tank decors. Some decors may have sharp edges that may ruin the delicate fins of your fish. If you decide to add driftwood (or bogwood) and live plants, choose them with care. Not all plants may be suitable for your fish. As for the driftwood, you should first soak it for several days before adding it to the tank, as adding them without pre-soaking will lower the pH and stain the water. Avoid using objects collected from the wild unless you are sure they are completely safe for aquarium use. It's best that you use objects bought from the aquarium store.[4]

Mistake #6: Over-cleaning the tank

I've heard from another fish owner that he would clean the tank everyday and perform 100% water changes. Sad to say, his fish didn't last long. Cleaning the tank excessively removes the good bacteria that provides a stable living condition for your fish. You don't want to disturbed the already established water condition for your pet. Instead of performing complete water changes, do a weekly to biweekly partial water changes. As to how much water to remove, that differs from tank to tank. I personally perform a 10% water change once a week, as my cichlids are very dirty eaters. Adding decors may be a good idea as they help trap more good bacteria. 

Mistake #7: Keeping Fish in a Small Tank

Big Fish Small Tank
Credit: Praveen Gupta | Flickr

Keeping the fish in a small tank will restrict their growth.

A large tank is better than a small tank. It allows more room for mistakes. Committing the mistake of adding a different temperature of water, for instance, can provide minimal harmful impact on the fish if the tank is large. It's also nice to see a fish swim around and keeping it in a small tank will only restrain their movement and stunt their growth.
To find the right tank size for a particular fish, here's a quick rule of thumb: Every inch of fish requires one gallon. Messier fish, such as cichlids and goldfish,  require three or more gallons per inch.[3] So if you plan to keep a three-inch fish (non-messy type), the tank size should hold at least three gallons of water.

Mistake #8: Not Learning Enough About the Fish

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Before you bring home your pet fish, do a research about his likes and dislikes. What food does he like? What is the ideal temperature of his tank water? How about the ideal pH? Does he like plants and decors? Does he like to have a companion? Is he carnivorous, herbivorous, or both? What is the required tank size for the fish to be happy? Finding out about the fish's requirements will help you create an environment that will make him happy and healthy.

Mistake #9: Placing the Tank at the Wrong Location

Credit: glasseyes view | Flickr
The venue of the tank matters to your fish. If you place it next to the window, algae will start to invade the tank. If you place the tank along the walkway, the fish may get stressed out by all the people passing by. Give the pet a location where she can feel safe and comfortable.
To find the best place for your tank, consider a venue where it is least likely to get bumped at. Find a location where you can conveniently clean it, preferable near a water source. Avoid setting the tank near any heating or cooling devices that would influence the temperature of the water.[5]


Apr 30, 2015 9:44pm
Agree with all of the above, after keeping fish and koi for many years. So many chemicals in the water from our taps these days, harmful they say even for us humans. Correct filtration is very important too. Rated up
May 3, 2015 7:12pm
Thank you for leaving a comment and rating. Indeed, the quality of water is crucial for fish health (and also for us humans). Kois are lovely creatures. I wish I have one but I don't have a pond.
May 2, 2015 12:25pm
Excellent pointers--my wife's son recently took on a tank situation with about 10 very small fish in it (they're all named "Kevin"), but he's been pretty good about keeping up with them, keeping the tank clean (on a schedule, not daily as the bad person you noted did) and not overfeeding them. This was a good primer for those wanting to consider freshwater fish as "pets" (?, I'm never really sure if I should call a fish a pet or not). Anyway, thumb's up!
May 3, 2015 7:15pm
Thank you, vicdillinger. I'm glad to hear that your wife's son is a very responsible fish owner. I'm sure the ten Kevin's are very very happy.
May 4, 2015 7:26am
Thank you for leaving a comment and rating. Indeed, the quality of water is crucial for fish health (and also for us humans). Kois are lovely creatures. I wish I have one but I don't have a pond.
I have seen Koi in ponds and lakes. I believe they get too big for the small backyard ponds and people just transfer them to other bodies of water. I've actually caught 2 of them in my lifetime while fishing for carp.
May 5, 2015 6:39pm
Hi RaymondE. I've never seen a Koi in the natural environment. Some of my friends have backyard ponds with Koi. I hope those ponds are large enough to accommodate the fish. So far, they look happy living there.
May 6, 2015 1:36am
I think that they were put in the pond by someone who either got tired of them or they out grew their environment. The pond is large enough to sustain twice as many koi and carp that it currently holds.
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  1. "Beginner FAQ: Water Treatment." The Fish Information Service. 6/03/2015 <Web >
  2. "Why Overfeeding Fish is a Problem and How to Avoid It ." Pet Education. 6/03/2015 <Web >
  3. "How Many Fish Can I Keep." The First Tank Guide. 6/03/2015 <Web >
  4. "Aquascaping ." The Aquarium Wiki. 7/03/2015 <Web >
  5. "How to Select the Best Location of Your Tank ." Rate My Fish Tank. 7/03/2015 <Web >

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