Fish Tank Problems from 25 Common Mistakes

Starting a new thing is quite thrilling and, at the same time, a bit challenging. So if you plan to begin fishkeeping, I’ll advise you to prepare with the necessary knowledge. People indeed learn a great deal from their mistakes in the practical field. But if you upskill yourself with proper theoretical knowledge before the start, it will keep down blunders.

I have been in this fishkeeping arena for long 15 years and am quite familiar with the beginner’s mistakes from my own experience. But they are avoidable if you follow a few simple tips. I compiled 25 common errors that cause fish tank problems for newbies. In this article, I will share those learnings with my newcomer friends who will be new members of our community.

Here They Are

1) Starting Without A Proper Plan:

A jumpstart out of excitement but without proper planning is a great mistake that many would-be fishkeepers make.

Planning is the key to success. Make a thorough plan before you start. You should know your aim, what type of aquarium you want to have, and the types of aquatic pets you prefer.

You should contemplate your budget and think about how much time you can spend on the hobby. Your planning will be the basis of all your next step decisions.

2) Buying A Small Tank:

A common misconception that exists about fishkeeping is that a smaller aquarium is easier to maintain. But it’s not right for all cases. For example, if you are planning to have a community tank, you should start with a 20-30-gallon tank, at least.

Still, you can start with a 10-gallon tank, but be picky for fish selection. There are some fish pretty comfortable to keep in a nano tank. You can check my article on the best fish for 10-gallon tanks.

Larger aquariums are more manageable to keep stable, and you’ll get sufficient time to take corrective actions if things start going wrong.

3) Buying The Aquarium And Fish on The Same Day:

Starting a new thing is so thrilling that you can’t hold the temptation to get everything ready quickly. And so people make this common mistake.

You completed setting the aquarium and filling it with water doesn’t mean the aquarium is okay to add fish just after the installation work.

I strongly recommend not to buy the aquarium and fish on the same day. It would help if you had a few days and even weeks to make an aquarium completely ready to add fish to it.

4) Not Cycling The Tank Properly:

Establishing a nitrogen cycle in an aquarium is crucial. This cycle is a biochemical process consisting of several steps. Aquarium wastes produce ammonia, which is extremely toxic and deadly for fish.

Luckily, the nitrogen cycle is a process that converts ammonia to nitrate through a multistage reaction. Nitrate is not as acutely harmful as ammonia to fish.

So, you have to cycle the tank properly before adding fish to it. The water testing result will indicate the status of the cycling process. In a cycled tank, the ammonia and nitrite level tends to be zero. 

5) Not Quarantining New Fish:

I will advise you to start a brand new fish tank with a few starter fish. Then, after complete cycling, you can bring more fish. Adding newly bought fish directly to the main tank is another common but crucial mistake.

Fish in the pet store share tank with other fish and can carry diseases. Besides, newly bought fish are under the stress of transportation and condition change. That’s why they need a quarantine period in a separate tank so that they settle themselves and you can closely monitor them.

Quarantining fish is essential for new tanks and anytime you bring new members to your existing aquarium.

6) Wrong Fish Selection:

The fish selection is the area where most newbies become misguided. The proper fish selection is vital for the excellent outcome of an aquarium journey. The compatibility is the primary concern if you wish to make a community tank.

Not all fish are compatible with each other. Some are aggressive and territorial, while some are weak and peaceful creatures. Some fish are predatory carnivores, and some are perfect to be their prey. You cannot keep a lion and a ship in the same cage.

Besides, a beginner should select fish that are hardy, low-maintenance, and easy to keep. You can read my article on the best freshwater aquarium fish. You will get several fish here suitable for beginners.

7) Overstocking:

Overstocking is the most common mistake by beginners, I’ll say. Unfortunately, overstocking is very harmful to fish’s health. A general rule of thumb is that the tank gallon number should be the total length of all fish in it. However, you must be specific and find the ideal stocking amount for your aquarium size.

For instance, in a 20-gallon tank, you can keep twenty 1-inch fish or ten 2-inch fish in general. However, this linear calculation doesn’t apply when fish size increases. Like all other experts, I advise beginners to keep less fish than this thumb rule. Your opening will be very smooth if you don’t overstock.

8) Careless About Water pH:

pH level is the primary indication of the aquarium water’s healthiness. Many factors can affect the water condition, and water pH reflects that something is wrong regardless of the cause. Testing water pH with kits is very easy and takes hardly two minutes.

People skip this step as they think it’s extra work when everything is going fine. I will advise you to test the water parameter, especially monitor pH frequently, not only in the initial stages of your journey but also at any time.

Related Topic: What are the causes of high and how to adjust it

9) Not Maintaining An Ideal Water Temperature:

The ideal temperature for most tropical aquarium fish lies between 75 to 80 °F. At a lower temperature, fish are more susceptible to fungal and bacterial infection.

Especially for newly bought fish, maintaining the right temperature is vital, as they are going through the tremendous stress of tank change and transportation. The disease can easily catch up in stressed fish.

10) Inadequate Cleaning:

Cleaning is the most laborious job required in aquarium keeping. But cleaning is crucial, especially during the initial stages of the aquarium journey. Many factors exist in a new tank to contaminate the water.

Dust comes out from the substrate to make the water cloudy, and dyes from decor can discolor it. Most importantly, a new tank may not be fully cycled, which results in toxicity buildup.

Frequent water changes are essential for the newly build aquarium tank. I’ll suggest you replace one-third of the water twice in the first week. After that, the frequency will be less gradually. Still, 10 to 20 % of water change every week is a good practice.

It is advisable to replace the filter media weekly for new aquariums. Once everything is stabilized, you can set the filter changing frequency as bi-weekly.

11) Overcleaning:

You already know about tank cycling. Some beneficial bacteria promote the nitrogen cycle while they build colonies in the substrate or the filter media. However, vigorous cleaning and sweeping water changes may purge all the helpful bacteria that keep the aquarium clean and healthy.

The right balance is vital. You may observe cloudy water more often at the initial stage of a new aquarium. But never replace all of the water, desiring complete cleanliness. Especially in a new aquarium with a partially-developed nitrogen cycle, beneficial bacteria are invaluable.

12) Lack Of Adequate Filtration:

Sometimes people are happy with having a high-tech mechanical filter in their aquariums. But a mechanical filter eliminates only undissolved solid particles and nothing else. Impurities in water exist in many forms.

A complete filtration unit should include three stages consisting of a mechanical, chemical, and biological filter. Especially having no biological filter in the aquarium is a great mistake. A biological filter helps to grow must-needed beneficial bacteria.

13) Too Frequent Rearranging:

Not being satisfied with the starting arrangement is another common newbie syndrome. They want to get everything perfect following their aesthetic preference. Bought a few decors? After some time, you feel it’s not that beautiful, and you want it in another way.

It’s a prevalent human instinct, but you should avoid frequent rearranging the aquarium items. New fish are struggling to cope, and this frequent change can impose more stress on them.

14) Overfeeding:

Overfeeding does no good to your beloved pets, but it harms them in many ways. You should provide as much food as fish can finish in 2-5 minutes. Food leftovers sink and accumulated in the substrate.

Heavy eating does not ensure extra nutrients for fish, but they produce more poops by excess eating.

Accumulated food leftovers and wastes produce toxic gas by decomposition. So, overfeeding can adversely affect the cleanliness and health of the aquarium.

15) Overdosing Medicine:

Overmedication can be deadly for fish. So, I advise not to dose medicine without having proper knowledge of it. Even, if you are sure about the pet’s sickness or have taken a prescription from a vet; you should take sick fish to a separate tank and then only treat them.

Similarly, while dosing any water care chemical, follow the manufacturer’s instructions to the letter.

16) The Wrong Substrate:

The substrate is an essential item to establish a healthy aquarium. But a beginner should choose a substrate carefully. In my opinion, crushed gravels of medium size are the best substrate for beginners.

Large pebbles create more gaps inside the bottom bed, hence very difficult to clean. Aquarium wastes get trapped inside the substrate and result in water pollution. It would help if you avoided dyed gravels/pebbles because the artificial dye may dissolve in the water.

The second best option is to use good-quality aquarium sand for the substrate bed. However, cleaning the aquarium sand can be tricky, and a beginner with no hands-on experience may find it difficult.

17) Unsafe Decors:

Decors are ornaments for the aquarium. An aquarium is not only the habitat of your aquatic pets; it’s a showpiece to beautify your place. So every aquarium owner wants to have gorgeous decors so that his aquarium looks pretty.

But beginners often make mistakes to focus only on the visual appeal of decors. Decors may be unsafe for fish. Harmful dyes or chemicals in the decor can contaminate the water. Or, if you don’t choose a finely polished item carefully, sharp edges may exist to injure fish.

18) No Live Plants:

Having no live plants in the aquarium is not actually a mistake. Instead, I will say it’s a great miss of opportunity. But, I will not suggest newbies start with fish and plants at the same time. 

Live plants can establish a natural healthy biological cycle in an aquarium. Plants consume toxic products such as ammonia, nitrates, and carbon dioxide, and on the other hand, add oxygen to the water. Thus live plants keep the aquarium condition clean in a natural way.

Having live aquatic plants is an excellent idea, but it requires some expertise. But it would help if you had live plants in the aquarium when you are no more a novice.

19) Over Lighting:

Lighting is essential if you have live plants in the aquarium. Fish, on the other hand, have no biological need for light. In the beginning, most newcomers introduce a lighting system to enhance the aquarium’s visual beauty. But too intense lighting has adverse side effects. 

Sometimes people keep the aquarium light on for 24 hours, but overlighting promotes algae growth. Instead, you should keep your fish tank light off at night. Excess algae in the tank cause oxygen deficiency and cloudy water, which upsets fish’s health.

20) Improper Regular Maintenance:

Even for seasoned aquarists, a proper schedule for maintenance is mandatory for smooth aquarium keeping. However, having no fixed plan for regular maintenance is a mistake.

It would be best if you had a proper schedule for filter media replacement and water changes. In normal conditions, you should do these tasks every other week. Additionally, it is better to have a plan for water-care chemical dosing, vitamin supplementation, etc.

21) Not Having A Power Outage Plan:

Power outages or any other failure can cause accidental poisoning. We don’t have control over an accident, but we can minimize the consequence with a proper mitigation plan.

Due to a power outage, the filter and the air pump can stop working. For a prolonged shutdown, the outcome may be fatal. Fish die if the oxygen level drops. Likewise, filter media can be poisonous if kept turned off for a long time.

So it would help if you had a backup plan of power supply or any alternative method to add oxygen. It is advisable to replace filter elements during a long time service outage to prevent poisoning.

22) Compromising Quality For Money:

Budget matters! But you should not compromise the quality, especially for fishkeeping products. Often beginners suffer from buying low-quality products. As they have only a little idea about the new field, first-timers are misguided easily.

Many products in the market are cost-effective, at the same time, reliable. I’ll suggest taking an expert’s advice or going through dependable review posts and buying guides before purchasing.

23) Taking Advice From A Layperson:

Knowledge is power if it is authentic. Wrong guidance can mislead you into the darkness. The same thing may happen in the fishkeeping arena. It would help if you were wise while gathering information. Don’t trust anyone blindly, but always crosscheck and verify.

People can misguide you to fulfill their commercial interests. For example, sometimes, pet shop owners’ advice is only for their business and not for their well-being.

So, I am advising you not to take advice from anyone. Instead, always seek help from an expert or a trusted friend before taking any crucial steps regarding the hobby.

24) Obsessed Over The Hobby:

Obsessing over fishkeeping is harmful to the hobby indirectly. If you are obsessed with it, there is a chance of making mistakes. Obsession increases the possibility of an impulse decision that may turn wrong in the end.

An aquarium needs some alone time for stabilizing as an ideal fish habitat. But, unfortunately, your obsession can disturb its much-needed alone time.

Obsessed people get dishearted and demotivated easily, and their initial excitement may end up a heartbreaking experience.

25) Lack Of Patience:

All good things take time to flourish, and this fact is very much applicable to aquarium keeping. Nothing changes overnight here. Initially, it takes 4 to 6 weeks to get a stable aquarium condition.

The owners habituate fish in a regular diet schedule, and this practice also takes time. Fish won’t learn manners within hours, and your fish won’t grow up within days.

Not only for noobs but patience is required in fishkeeping for seasoned members also. So keep patience, and your patience pays off at the end of the day.

Final Words

Fishkeeping is a fantastic hobby to give satisfaction and relaxation that a few other hobbies can. You can have great fun and pleasure time with pretty colored fish. They can bring more color to your life.

Besides, fishkeeping is one of the low-hassle hobbies, but many people don’t know it. So you have to know the tricks only, and then it’s just straightforward.

People have some misconceptions about this hobby. When you decided to be an aquarist, you have to know the fundamental things of fishkeeping.

I tried to shed light on a few essential tips to avoid fish tank problems after starting a new hobby. Don’t hesitate to share your experience and put a comment in the below comment box.