Illustration of a larger tank vs a smaller tank

Many of us in the hobby probably started out with a smaller tank, eventually upsizing to a larger aquarium that could keep almost anything we wanted. However, down the road some of us may have found out that the larger tank is a lot of work. Some of us with our significant other discovered the electric bills have gone up from all the equipment running on it. Maybe some have had to move to a smaller home where their larger tank wouldn't fit. Some even just wanted the challenge of keeping a smaller tank or to take advantage of them being easier to carry, easier to install, being cheaper to stock, equip, and run. Whatever the reason may be some times call for a downsize to a smaller tank. If any of these scenarios are hitting close to home, here are a few tips and guidelines that may help you.

Prepping the New Smaller Tank:

In the downsize process to a smaller tank, it is highly recommended to start from scratch with new rocks, sand, and media to prevent cross contamination of pest or nuisance algae. Setting up:

  • Move the new cabinet or stand into place.
  • Adjust its feet or use leveling shims to ensure the new cabinet is level.
  • Place the tank onto the cabinet with a leveling mat. Check levels.
  • Install the plumbing, return pump, heaters, powerheads and lighting.
  • Place new rockwork in - pre-planning the aquascape is suggested.
  • Add new clean sand.
  • Add new saltwater.
  • Begin preferred method of cycling the aquarium.
  • Test parameters - once ammonia and nitrite levels drop to zero and the nitrate becomes present, it is safe to start adding animals into the aquarium.

Breaking Down the Old Larger Aquarium

Before getting started, there are a few things to have on hand before moving to a smaller tank:

Infographic of tools to have on hand to breakdown the larger aquarium and into the smaller tank

  • Containers or buckets to move everything from the existing aquarium into.
  • A siphon to transfer as much clean water possible into the containers.
  • A net to catch the fish and then place them in the containers of water.
  • A small submersible pump, powerhead or air pump with air stone to keep proper gas exchange in the containers. Air stone would be preferred when moving tanks, since many fish often suffocate during tank moves.
  • A heater to keep temperatures stable.
  • Plenty of towels.
  • Optional: A tight-fitting lid on the vat the fish are being moved into to prevent any jumpers and to reduce stress

Breakdown Process:

  • Turn off all equipment.
  • Siphon out "clean" water from the old tank into containers, buckets, or another old fish tanks large enough to hold fish, coral and rock.
  • Remove or frag coral from rockwork and place into their own container. Due to their ability to release toxins when under stress, a separate container is highly recommended.
  • Remove rockwork and place in a separate container. Removing rock makes catching the fish easier, just check that there are no fish stuck inside of the rockwork.
  • Catch the fish and invertebrates, placing them into a container of "clean" water with a heater and an airstone.
  • Put a tight-fitting lid over the fish container to keep them from jumping out and to reduce stress levels.
  • Discard the leftover dirty water and sand from the old tank.
  • Drag the old tank out of the way, vacuum, dust, and clean the area the large tank occupied.

Separation of fish and coral to move into a smaller tank

After breakdown, even though it would be nice to move over all the fish and coral from the larger tank, the reality is that the downsize will not be able to support the large bioload. It will also not be enough space for any of the larger fish species. Large coral colonies may need to be fragged and freshly mounted into the smaller tank. Many (if not all) of the fish and coral may need to be sold, given away or brought to your local fish store for credit. Rock and sand may need to be discarded, dried out (for storage) or sold off.

Dos and Don'ts with Small Tanks

Final setup of a smaller aquarium stocked with frags and small fish

If starting the new smaller tank with all new livestock, only stock it with a few small fish introduced weeks apart so the aquarium can adjust. Avoid territorial fish like damsels or large active fish like surgeonfish. Small reef tanks still need a skimmer, ATO, powerhead(s), and supplements if you want to be successful. Small tanks can heat up and cool down very quickly so use a temperature alert and be prepared to use a fan or mini cooler in hot weather. Abrupt changes to the tank can shift parameters quickly, so be aware when adding supplements, media, fish, etc. - smaller tanks are less forgiving than larger tanks.

Things to Keep in Mind for Tank Moves

Take your time, be patient, stay calm, and give yourself all day to downsize to the smaller tank, because some tasks may take longer than expected, so think of a goal finish time and add extra hours to it. Invite a fellow fishkeeper over for help, input, assurance and to move things along quicker. Start early, and have backup equipment or be sure your local fish store is open within your goal finish time in case anything goes wrong.