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Top 10 Fishkeeping Myths
Published by Fishy-Fishy on 26/10/2006 (20536 reads)

There are many old wives tales relating to fish care, some of which are potentially damaging if they are believed! This article aims to clear up the fact from the fiction and half-truths to give new fishkeepers a bit of help starting out.

1. Fish only grow to the size of their tank.

The biggest and worst myth of them all! If this were true, I would have my very own great white shark and possibly a small shoal of barracuda swimming around my 37 gallon tank. Of course, this ‘fact’ which is all too often quoted by some pet shop staff, is totally untrue and has led to many fish being kept in cramped conditions. So where did this myth come from? Some fish will become stunted in a too-small aquarium. Although it appears that they have grown to the size of their environment, the fact is that they will have health problems caused by the stunting and as a result will have a much shorter life expectancy.
To prevent this from happening, always research the potential size of the fish you are getting and plan accordingly. Remember that most of the fish you see at your local fish shop are juveniles and are likely to grow much, much larger!

2. Fish don’t live long.

Leading on from fish myth number one is this little ‘fact’. New fishkeepers are often pleased when their goldfish lives for three years because they believe this to be a ripe old age for their pet. The truth is that most fish will live for at least 5 years, and some- including goldfish- will live a lot longer. There are a few exceptions to this rule, notably killifish and Siamese fighting fish which will usually live for less than three years.
To ensure your fish fulfils their potential life span, make sure you provide everything they need including a spacious tank with filtration and suitable tankmates if required.

3. It’s OK to keep fish in glass fishbowls.

Although these traditional glass bowls are still sold in some pet shops they do not make a good home for any kind of fish. There are two reasons for this; firstly, bowls tend to be very small compared to tanks and just don’t hold enough water. Secondly, bowls have a small surface area of water compared to their volume. A large surface area is important for gas exchange to take place. Even though fish live in water, they still need oxygen or they will suffocate just like us.
A rectangular or square aquarium provides a much larger surface area and is a much better choice than a bowl or round aquarium.

4. Filters are just a gimmick; fish don’t really need one.

No, it’s not just the shop staff trying to make a few extra pounds- your fish really do need that filter. Fish live in their own waste and so you need to keep the water as clean as possible to prevent health problems. A filter will help convert the harmful ammonia produced by the fish into less harmful nitrite and then into nitrate.
There are many different types of filter to choose from that will suit different tank sizes. A bit of research should help you choose which one is right for you and your fish. A filter should ideally provide mechanical and biological filtration to keep your water in top condition and your fish happy and healthy. Marine tanks will need additional equipment.

5. If you have a filter you don’t need to change the water in the tank.

Sorry! This one isn’t true either. While it may be true that a filter means you don’t have to change the water as often, you will still need to change it. The nitrate (NO3) in the water should be kept below 50ppm (lower in marine tanks) and this can only be done by doing regular water changes. Testing the water will help you figure out how often to do a water change and how much needs changing. Be sure to check the NO3 content of your tap water as in some areas in can be quite high and if you do live in one of these areas your fish may benefit from reverse osmosis (RO) water which should be available at your local fish shop.

6. The guy in the pet shop told me something so it must be true.

What the shop staff told you may very well be true. A lot of staff are very knowledgeable and helpful. Unfortunately, just as many are untrained and unqualified to give advice on fish care. To beginners starting out in the hobby, shop staff are the first port of call when looking for advice. While it is a good idea to ask if you are unsure of something, I would recommend doing additional research as well to be sure that you are arming yourself with enough information.
If you are unsure about how qualified the staff are at your local fish shop, ask them if they keep fish themselves and if they have any fishkeeping qualifications. Good shop staff will take the time to explain things and make sure you fully understand, and they won’t tell you any of the myths in this article!

7. Catfish will help keep the tank clean.

This is another one with an element of truth- most catfish are scavengers that will ‘hoover’ up any food that is uneaten by the other fish. Certain species of catfish will eat some of the algae off the glass and ornaments, making your job a bit easier. However, no catfish eats the waste of other fish so you will still need to keep up a regular cleaning regime no matter how many catfish you have.

8. Fish have very short memories and are stupid.

Everyone’s used the phrase ‘a memory like a goldfish’ to describe someone as forgetful- but how short are their memories really? Do they really only remember things for 3 seconds? No, this is another myth. Anyone who keeps fish will tell you that they remember when dinner-time is! And it took my goldfish fry approximately 10 days from hatching to figure out that me standing next to the tank means that it’s feeding time. Fish will very quickly learn to associate humans with food and as most fish have good eyesight they will see you from a short distance away. You may notice them come to the front of their tank when you enter the room, begging for food- hardly indicative of a three second memory.
Scientists have performed many experiments to test the intelligence of fish and have found that fish are often underestimated. Some scientists believe that fish can recognise their owner and may even miss them while they are away on holiday.

9. It’s OK to keep bettas in a vase, they will eat the plant roots and the plant will keep the water clean.

Nooooooo! Avoid betta vases like the plague. Bettas are insectivores so will only try to eat the plant as a last resort. If you were starving to death, you’d probably try to eat whatever was around too. A wild betta’s diet consists almost entirely of insects and insect larva and in the aquarium they should be fed betta flakes, freeze-dried, frozen or live food.
These vases are also much too small for bettas. It is often said that bettas can live in bowls because they live in puddles in the wild. This is another myth- bettas can survive in puddles in the dry season, but live and breed in slow-moving streams and rice paddies which are huge!
As for the plant keeping the water clean, the plant will absorb nitrate from the water but this won’t help the poor little betta survive. The plant will also block the betta’s access to the surface of the water. Bettas are labyrinth fish, meaning that they have a special organ that allows them to breath air from the surface, but if they can’t get to the surface that spells bad news for the betta.
Bettas will be much happier in a small aquarium where they can swim around and eat proper food. A 5-10 (UK) gallon tank all to themselves is the best home for a betta.

10. Fish are boring.

Well I guess you could say this one is a matter of opinion but I say it’s WRONG!! Fishkeeping is a hobby that is so easy to get completely lost in and it becomes an obsession for many people. There is so much to learn that you will never get bored if you feel the inclination to study your fish in more detail.
A lot of fishkeeping is opinion and experience rather than scientific fact- add to that the fact that new fish are being imported every month and that gives you a very real chance that you will make your own discoveries about fish.
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  • Marine  Adviser


brilliant article fishy-fishy! if only shops had a copy as a poster or something!

  • Home away from home

 Re: brilliant!

we should all print this off and take copies to our lfss now!


 Re: brilliant!

Great artical! fish are not boring

  • Just popping in



This is brilliant, so useful and straightforward. I wish that I had read this before I started. Is there anyway this can be put somewhere when newbies like me can see it as soon as we start to look into starting this (absolutely fascinating) hobby. Not in the least bit boring.

Thanks again

  • Home away from home

 Re: Thanks

I went into a fish shop (can I name it?) that had bettas in vases and little display cubes. I don't know much about Bettas as I keep coldwater fish but I did think that this was wrong. I didn't have the confidence to say anything in that shop, but I asked about it in the next shop we went to. They didn't have this type of display but unfortunately, they did tell me that it wasn't particularly cruel to keep Bettas this way as long as water changes were frequent.
I am relatively new to fishkeeping but because of this experience, I will never, never rely on anything a saleperson in a fish shop tells me.
One question though, could I keep one betta with a small shoal of neon Tetras in a 6 gallon tank?

  • Home away from home

 Re: Thanks

Must have missed this, first time I've read it.
Wonder how many fish would avoid suffering and death in the UK if this simple leaflet was handed out in lfs to all new fishkeepers.

I'm going to print this off and show it to my family. They think I'm off my head spending time testing water, researching fish species, travelling to other towns because I refuse to buy fish at P@H.
Of course, they refer to the goldfish we had as kids that lived "Happily & Healthily" in a small, unfiltered tank for 3 whole years.

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