Second Hand Fish Tanks

From time to time, second hand fish tanks come up for sale.

Usually the previous owners have either upgraded to a larger tank, downgraded to a smaller one, or have given up the hobby completely.

The fate of a fish tank follows the fortunes of the fishkeeper!

(How’s that for alliteration? Remember, you read it on first!)

Whether it is a ready-made tank or a custom built one, a used fish tank in good condition goes for about a third or even a quarter of its original price. Sometimes you can even find a tank being given away. Most people would be leery of those, but if you know what to look out for — and this applies to any used tank — you will be able to make a good choice.

Second Hand Fish Tanks | Ask The Right Questions!

When considering a used tank, it important to ask the seller a few important questions. It will give you a feel for what you’re getting into. But much like buying a used car, don’t always expect a straight, honest answer!

How long has the previous owner had the tank and how long has it been running?

The most obvious question, but a pretty important one. While I’ve seen glass tanks that have been around for 15 or 20 years (my own tank has been in faithful service since 2005), I would generally steer clear of second hand fish tanks older than 5 years.

A 5 year old glass tank would show more than its fair share of scratches from algae scrapers and cleaner magnets. And although it is not my experience, some will say that 5 years is also about the time when you will see the beginning of deterioration of the seal between glass and silicon.

There are other variables involved of course, other than the age of the tank, as we will discuss below, so if you happen to come across an older second hand tank in really good shape, and the price is right, why not?

Has the tank been stored away dry?

A glass tank stored dry in a garage for a couple years — or worse, left out in the open and under the sun — is bound to have hardened silicon joints and is bound to develop leaks over a very short period of time.

Here’s a simple silicon test: run your finger along the inner seams of the tank and feel the silicon. It should feel soft, pliable and rubbery. If the silicon feels hard and dried out, I would advise you to politely walk away.

Why is the owner selling the tank?

A very important question, and one well worth asking!

As I mentioned at the start of this article, second hand fish tanks come up for sale because the owners are upgrading to a larger tank, downgrading to a smaller one, or giving up the hobby altogether. But there is also the odd seller who is getting rid of his tank because of some inherent problem. I once came across a forum thread where someone had bought a used tank setup where the sump in the system was too small — it would overflow when the return pump was turned off!

Has the tank been repaired or modified in any way?

I would generally stay away from any tank that has been repaired, unless the repair was professionally done. Look out for extraneous lines of silicon on one of the inner or outer seams of the tank — a sure sign of a DIY attempt at plugging a leak.

A Useful Tip When Considering A Used Acrylic Tank

Bring a small piece of white paper, hold it on the inside of the tank while looking at it from the outside. Older acrylic tanks may have yellowed with age, and it is not something that is immediately obvious until the tank is filled with water and the aquarium lights are turned on. If the white piece of paper appears yellowish when viewed from outside the tank, you will have a good idea if the acrylic has yellowed, and to what degree.

Prepping Your Newly Purchased Used Fish Tank

Place and setup your newly acquired tank as discussed in the Ideal Location For Your Saltwater Aquarium In Your Home.

Hook up the return pump to the plumbing and fill the tank with tap water and let the system ‘wet-run’ for a couple of days. Letting the system run for two days will reveal any leaks and problems with the tank, sump and plumbing.

If no leaks are apparent, drain the tank completely and wash the tank and sump out thoroughly using a few handfuls of aquarium salt and a new, unused dish scouring sponge. Now would also be a good time to remove any old calcium and coralline algae deposits.

In the case of a used acrylic tank, you might want to buff out all scratches and scuffs using an aquarium-safe acrylic buffing compound. You will not be able to buff out any scratches once the aquarium is filled.

Refill the tank with deionized or RO/DI water, add salt and you’re ready to begin your new saltwater aquarium journey!


Links to more Saltwater Aquarium Setup pages:

Aquarium Tank Size | Length, Width And Height

Ready-Made Aquariums

Acrylic Aquariums

Custom-Built Glass Aquariums

Drilled Overflows Vs. Siphon Overflows

Aquarium Stands

Why Beginning Hobbyists Should Avoid Starting A Nano Aquarium

How To Setup A Nano Tank

Aquarium Chillers

Aquarium Lighting

Aquarium Sump


Aquarium Covers | Put A Lid On It!

Cooling Fans



What You Don’t Need For Your Saltwater Aquarium!

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