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The Importance of Aquarium Size

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The importance of aquarium size – by seriously fishy

Aquarium Size

The size of your aquarium is massively important.  When first starting out many people shy away from a larger aquarium thinking that it will mean more work to maintain.  However, this isn’t the case and it is much easier to keep fish happy and healthy in a larger tank.

Years ago it seems it was perfectly acceptable to throw a Goldfish into a bowl, add some water and away you go.  I would guess that not many of these poor Goldies lasted very long and the average lifespan of Goldfish dropped to a month.

Goldfish can grow to 14 inches long and pretty chunky, bigger in some cases, that’s about the size of a Chihuahua.  How would a Chihuahua do in a bowl?  Probably about as well as the Goldfish.

goldfish tank size

Choosing your Aquarium Size

Why is bigger easier?

If you’re new to aquariums it may be surprising to hear that larger aquariums are easier to keep, but it’s true.  If you have a larger tank, it contains more water (Durr), that means that any waste that your fish produce is more diluted.  So as long as your tank isn’t overstocked it means that you could go longer between maintenance/water changes.

Clearly, though your water changes will be larger and if your massive aquarium is full to the brim with fish then you may still need to do your water changes weekly.  However, this doesn’t need to be difficult either.

I have seen many people recently complaining about taking bucket after bucket out of their aquarium, then pouring bucket after bucket into their aquarium to fill it again.  Use a hose, it’s a million times easier.  Just ensure that if you have a filter its turned off (if external) or removed (if internal) until you are sure that the de-chlorinator is well mixed.

Make sure you add your de-chlorinator before filling so that it mixes straight away.  The chlorine level in your tap water is highly unlikely to harm your fish in such a short space of time, especially as the de-chlorinator is already in your tank. It will however quickly kill the bacteria in your filter, so make sure it is not in contact until the water is thoroughly mixed.

Make sure its a clean hose too!  I do not doubt that some will disagree with this, but if it wasn’t true then the Python aquarium hose wouldn’t exist.  Anyway, I should probably get back on track.

If you’re new to fishkeeping and you’d like to learn more about getting started, check out our guide on setting up your first aquarium.

What size aquarium do I need?

Choose an Aquarium Size that Best Suits Your Fish

If you’re looking at getting some fishy friends or adding them to your tank, a quick google search of (fish name) + minimum tank size should give you a few results. They may differ, so my best advice here is to go with the largest. It’s important to remember that what you are looking at is a minimum size, so that’s the smallest tank that they can live in.

Bigger is always better as they will appreciate the space, but it’s unlikely they will be the only things in there. Most aquariums have some decor in them, some plants, gravel/sand etc.  So if you go for the minimum size then as soon as you add anything to the tank you have now dropped below it.

The decor is important too, fish like to have things to swim around, places to hide and it’s better for you too.  Having a bare aquarium with a couple of scared-looking fish hiding in a corner doesn’t make for great viewing.  So the best advice I have is to go for the biggest tank you can afford/fit in the space available. Chances are that if you don’t, you’ll only be looking for a bigger one soon anyway.

The fish that you are going to put into your aquarium come from lakes and rivers in the wild where they would have almost limitless space to explore, so the better we do to recreate that in our homes the better.


What happens if my aquarium is too small?

The Right Aquarium Size Will Help Your Fish Thrive

If your aquarium is way too small, it’s unlikely that your fish will live very long.  There is a common myth that fish only grow to the size of their environment, but it’s not strictly true.  There is some truth in it, fish growth will certainly be stunted by being kept in cramped conditions, but only their body will be stunted.

Most fish grow for their entire lives and whilst their body becomes stunted, their organs will continue to grow.  I’m sure you can imagine the grim end this leads to (Poor Goldies).

So, tank size is important, if you’re a few litres out then its unlikely to cause huge issues, but at minimum tank size and below, your fish may survive, but certainly won’t thrive.

When considering aquarium size, put yourself in the fishes fins; If you were him/her, would you be comfortable in a box that size?


aquarium size


About the author

James @Seriously Fishy

I am a fish keeping enthusiast with over 20 years experience. I currently keep American Cichlids (CA) which are my favourite fish to keep so far. I started Seriously Fishy as I noticed a large volume of people on various web pages looking for help with Aquarium basics. I created the first Seriously Fishy book to solve the issue in 28 pages, that led to the Seriously Fishy UK fish forum and blog.

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