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A guide to buying a used Aquarium

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A guide to buying a used aquarium.

My Latest Project

Purchasing a Used Aquarium

Yesterday I went out to buy a used aquarium as I thought it would be interesting to start a project and to expand my fish keeping capacity.  So this is an ideal time to write about what to look for if you’re buying a used aquarium.  Buying second-hand certainly has its perks, often the aquarium has been used recently so it’s already cycled, and there is a huge bonus on your bank balance, as it will cost far less.

Buying second-hand doesn’t come without risk though, and there are many things to look out for when you’re shopping for a used aquarium to ensure that you are actually getting a good deal.


used aquarium



The Tank

The aquarium is arguably one of the most important pieces to check thoroughly when you’re buying a used aquarium.  Its ideal to (if you can) view the tank both whilst it’s full, and when empty before you buy it.  Viewing the aquarium full and running gives you a bit of confidence that it all works, and that the aquarium is watertight.

The worst thing to happen would be to get home, spend hours setting it up, only to find it won’t hold any water.  I understand it could be pretty time consuming to turn up to see a full aquarium, wait for it to be empty, view it empty and then take it.  So a good idea here is to ask for a quick video of the tank full to prove it is currently running.

Then wait for them to drain it to go and view empty and pick up. The reason that viewing the aquarium empty before pick up is that you will be able to see any damage to it much more clearly.  Whilst an aquarium is full of water it can look almost pristine, with only larger scratches being visible.

When it’s empty, all the scratches are visible.  This will give you an immediate idea of how well it’s been looked after.

If there are no visible scratches when it’s full though, it’s probably ok.  Another point to note here is to see the bottom of the aquarium too.  Aquariums are often decorated with heavy rocks or pieces of wood.  If they have fallen at any point then there could be damage to the base.  This could make the tank a ticking time bomb to disaster if it eventually gives in.

Scratches on the aquarium are not the end of the world.  They can be buffed out and there are products available to help with this in most pet stores.  A light scratch only affects the aesthetics of the aquarium and won’t cause any structural damage.


The Filter

The filter is probably joint in importance with the aquarium itself.  They can be as expensive to buy as the aquarium, so its worth fully checking before you buy one used.  There are several things to check with a filter, foremost being that it actually works.

This is where your pre-check of the aquarium, while it’s running, comes in again.  If you have seen it running then great.  If you arrive and haven’t seen it run, then a filter can be quickly set up in a bucket to test it.

Secondly, is the filter powerful enough for the aquarium size?  Most filters will have a model number and litres per hour or gallon per hour marked on them, so most are easy to check to ensure it is the correct filter for the job.  If not, you may need to do some research, or be prepared to buy an upgrade if you can’t figure out what filter it is.

Next up you need to know when the filter was last used.  If it hasn’t been running for a while, then you will need to start it from scratch and cycle it fully.  If it has just been unplugged for you to take away, then it’s good to go straight on the tank again and should remain cycled, providing it was cycled in the first place.  Which leads to the next question:

How long has it been used for?  Always ask if a filter has been running a while, with fish in, this will give you a good idea as to whether the filter/tank was actually cycled.  If so then it will save you a long wait for the cycling process to complete and you will be good to go straight away.

You can learn more about aquarium filtration here.



Heaters are really important too.  When it comes to heaters I would always recommend buying new, even if the tank you are buying comes with one.  Heaters are relatively inexpensive but if they are damaged or haven’t been looked after they can spell disaster if they go wrong.  So most of the time it is not worth risking a used heater.

If you need to use a pre-owned heater then give it a good check over;

Is it scratched?

Is the wiring in poor condition?

Are there any bubbles/droplets inside the glass?

If your answer to any of the above is ‘yes’, then don’t risk it.  Any damage to the heater is a risk, modern heaters are generally shatter-proof but they can still do damage to your aquarium if they blow.  Droplets of water inside a heater can mean that the heaters waterproofing has failed.  The inside of the heater is where the electric heating element is and electricity and water do not mix well.

The best bet is always to buy a new heater, so you know there is no risk.



Lighting is optional on an aquarium unless you have plants.  But really, we all want a good view of our aquarium, right?  So always check out the lighting too.

Is it LED?

Are any LED’s out?

Is it t5/t8?

Do the bulbs work?

Is it suitable for plants?

Is it bright enough to light the aquarium?

These are just a few things to check with whatever lighting comes with the used aquarium, ultimately if it works and lights the aquarium well then all is well, upgrades will come later.


Everything else

Anything else that comes with an aquarium is a bonus really.  Just make sure that it works before you take it and that you want to include it in your set up.  Otherwise, you’re just taking things to fill your house/garage/bin with.

The more you get though, the bigger the bargain, and if you’re not going to use something but it is useable, you can always sell bits on and get some money back to re-invest in the tank.


Project aquarium



Final checks

Once you have your ‘new’ tank up and running, it’s always good to confirm that it’s all running correctly.  That means testing your water regularly to make sure that the filter is working as it should, and is converting that nasty ammonia.


If you follow these few tips you shouldn’t have many if any, problems with buying a used aquarium, just don’t rush into it, there are always loads for sale and new ones pop up every day.


For more tips, why not take a look at our other blog posts. You can even post your own articles.

Have fun and show us your used tank projects by adding our hashtag to your photos on Instagram! #seriouslyfishyclub


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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