Fish tanks and all of the supplies necessary to run them can get quite expensive. Secondhand purchasing of supplies can then be a great way to save money. Often times “bundled” packages from Craigslist, Kajiji, or other such sites can be a huge money saver. Getting a tank, filters, lighting, stand, and some extras are sometimes offered by someone wanting out of the hobby can be a great deal, but it is also a gamble. Here are my tips to ensure your used fish supplies purchases are worth your while.

Evaluating a Second-hand tank

• Ask the person who is selling the tank what kind of fish/reptiles were previously homed in the tank.
  • Ideally, you’ll want a setup that was used for the same type of ecosystem. Using reptile and marine/salt/reef tanks for freshwater systems can introduce disease or contaminate the water if not properly and thoroughly cleaned prior to use.
• Ask why they’re getting rid of the tank.
  • If the previous fish all died mysteriously, it could be that you’ll pass the disease or contaminant along to your future inhabitants. If they’re moving, you might be able to talk them down in price just to get the tank gone. If they upgraded to a larger system, you might be able to get further advice or some extras thrown in that they won’t need any more for their new system.
• Get pictures of the tank currently and while it was running if you can.
  • Scratches or other damage are often easier to evaluate on a system that is lit, so getting photos of the tank while it was running let you see what damage will be visible while you’re running the tank. These photos can also help you better imagine the relative size of your fish and decor to the tank, see if the person seemed to keep the tank well maintained (low algae, properly stocked, healthy fish) and get an idea of the stand the tank used.
  • If they’ve broken down the tank prior to posting an ad, the photos can be good indicators of the current condition of the tank. Check for where they stored the tank while empty – tanks stored outdoors or on unstable surfaces could have developed leaks that the seller isn’t even aware of. See if the person bothered to rinse out the tank and any extras that come with it – white residue or cloudy glass could mean you have to spend a lot of time cleaning and scraping to make the tank useable.

Lots of calcium and nutrient buildup on the plastic areas – hard to clean

I would not want to be the one to spend a day or two scraping those sides clean with a razor blade

Badly scratched acrylic tank – will need a solid polishing before use

Dirty, overstocked tank – will need a very thorough scrubbing/scraping

• Always go see the tank in person before purchasing.
  • Sometimes a deal that looks too good to be true is. Check the tank thoroughly in person, looking for scratches, sealant peeling, and broken braces. Check the stand if it comes with the tank. If you can, have the tank sit on the stand and push on the stand to see how sturdy it is. If the stand is able to move with an unfilled tank on it, there’s no way you’ll want it holding up the tank when it is full.
• Barter
  • When buying a used tank, there’s a certain amount of assumed “fixing” or “improving” implied in most cases. While a torn seal, broken brace, or rickety stand don’t mean the tank is beyond repair, but they do mean you’ll need to work on the tank and have knowledge of how to fix the problems. See if the seller is willing to drop the price given the tank’s shortcomings. Often explicitly pointing out the problem areas can make the seller more open to a reduced price, especially if they are inexperienced or unaware of the problem.

Secondhand accessories

• For bundled tank/accessory packages, make sure that the accessories are appropriate for your future tank!
  • Some people sell packages with filters, heaters, lighting, or glass magnet cleaners that won’t actually work with the tank to which they’re bundled. Ask for photos/product names, and then double check their stats yourself online. Make sure that you have adequate filtration for your planned tank – some setups, like goldfish or cichlids, often need to be filtered at a higher rate than a properly stocked community freshwater tank. Check the the heater can reach the temperature range you’ll need given the water volume of the tank. Check that the light fixture fits on the tank with which it is paired and that it will be able to fit your lighting needs (i.e. will be bright enough for the planned tank while covering the desired areas of the tank). And be sure that the mag-cleaners will work on that tank’s glass/acrylic thickness.
• Filters
  • Quality filters that will typically withstand the test of time include filters from Fluval and Eheim. Other popular brands include Tetra, Sunsun, Marineland, and Aquaclear. Canister filters are generally more expensive but easier to maintain and more aesthetically pleasing that hang-on-back (HOB) for planted tanks.
  • Check the filter’s impeller mechanism (example shown below). This is the part that will move the water through the filter, so if it is damaged, clogged, or otherwise not in good condition, the filter might need a replacement part or have similar damage in other areas.
  • Check the seals on canister filters. There’s nothing more disappointing than finding your “new” canister filter leaks. Sometimes all you need to do is clean or replace the large O-ring seal. Sometimes there’s a bigger issue.
  • Ask the seller how often they cleaned out their filter, and what filter media they recommend for it. You’ll get to see if they knew their setup well, and might get some good recommendations or free samples of what to use in the filter.
• Heaters
  • The current favorite heaters tend to be designed with bodies out of shatterproof plastic or other materials. Possible bonus options include being submersible, having adjustable temperature, possessing an auto shutoff mechanism to prevent overheating, and showing on/off state through visible means like an indicator light.
  • Make sure the heater cord is long enough to reach your intended outlet.
  • Check that it comes with a mounting solution, and inspect the quality of the suction cups or other parts. You can often buy replacements online or in store for cheap.
  • Avoid heaters that show any indication of broken seals, water inside the heating mechanism, or brownish burn/overheating marks. Overheating is a common cause of heater destruction, and it can be hard to spot.
  • Always monitor your tank after installing a new heater. You never know if its broken or terribly calibrated, and could cook your fish while you’re not paying attention.
• Lighting
  • Know what kind of lighting you’ll need for your tank. Planted tanks sometimes need lighting that can’t really be supplied by T8 lights that come with most pet-store tank hoods. Planted tanks often do well with High Output T5 fluorescent or LED lighting. Not all LED’s are equivalent though. There’s really no substitute for going online and finding pictures of tanks using the light you’re considering.
  • Ask to turn the light on/off to ensure it works. The bulbs might be blown, or the problem could be a more difficult circuitry issue.
  • Make sure you can get replacement bulbs/LED’s. Some fixtures might be an odd dimension or need brand-specific replacement parts, which can make getting replacement lighting parts expensive or impossible. For instance, if you buy a fixture needing very long HOT5’s, shipping can be quite expensive, and finding bulbs in the typically desired 6500K light temperature a lot of trouble.

The Moral

Anything bought secondhand should be carefully inspected and thoroughly cleaned before use. Cleaning should be done with safe chemicals and always rinsed repeatedly with water once cleaning is done. Always monitor new equipment for the first few hours/days to be sure its really working as expected. There’s no substitute for vetting the secondhand item and its seller thoroughly before purchase. It’s the only way to avoid wasting money and time once you’re home and can’t return the items.