Transferring Fish to a Larger Tank

Transferring fish to a larger tank requires planning.

Q. How would I go about transferring a 20-inch pacu from an 80-gallon aquarium to a 300-gallon aquarium? I will have to tear down the 80 gallon, build a stand for the 300-gallon aquarium and then fully set it up (I intend to use the stand that the 80 is on as part of the stand for the 300). Could I use a clean 55-quart plastic cooler that contains water from the 80 to start with? It would have an air supply and I’d have the lid shut to keep it dark and calm for the fish.
Paul Roberts
Wichita Falls, Texas

A. Wow, that’s a good-sized fish you need to move! Prepare to get wet when you do it. Moving a large fish such as your pacu is not easy. Traditional fish nets are going to be too small for this fish. You might be able to catch it by hand, but there’s no way to do that without hugging it and getting soaked — and you risk injuring yourself or having the fish slip out of your arms and onto the floor, where it could get injured. I’d buy a landing net — the kind fishermen use — from the local sporting goods store. It would be large and strong enough to hold such a fish. Your fish will probably get slightly scuffed in the process, but there’s no avoiding this, and it should heal fine. Your pacu will be happy in its new aquarium.

The cooler sounds too small to me. A large plastic garbage can would be a better choice. It will hold more water and give the fish a bit more room. Covering it is a good idea. The fish should stay calmer in the dark, and the lid will keep your pacu from jumping out onto the floor.

A 300-gallon aquarium is going to weigh about 3,000 pounds — that’s a ton and a half. Make sure your stand is strong and that the floor can support it. I don’t know your stand design, but I have severe reservations about trying to incorporate an 80-gallon stand into a 300-gallon one.

Your stand should be flat and level, and it must function as a single unit. For example, having an aquarium stretch across multiple stands would be a bad idea because there would be stress on the aquarium at the junction between each stand.

I don’t know the dimensions of either your 80 or 300, but if this is a home-built stand, use long boards to tie it all together. So, if the 300 is 8 feet long, it should be resting on a platform made of 8-foot boards, not shorter boards bolted together. If you’re planning to stand two or more commercial stands side by side, this is a very bad idea. They each shift independently, and that can lead to cracks in the aquarium.

When you set up the new aquarium, use some gravel from the old aquarium to seed the biological filtration. Big fish put out a lot of waste, so you need those helpful bacteria to break down that waste. When your pacu has more room, it is going to grow and put out even more waste.

Adding water from the old aquarium may or may not be a good idea. Run water tests on it first. If tests show measurable ammonia levels, do not use the water. aquariums that contain large fish are often polluted. Waste build-up causes the pH to drop, which causes biological filtration to reduce and ammonia levels to climb (as the less toxic form, ammonium). The pH affects the toxicity of ammonia. Tough fish often survive this, but when you mix that old aquarium water with new tap water (which tends to have a higher pH), the rise in pH causes the ammonium to turn back into deadly ammonia and could kill your fish.

If there’s no ammonia, but the water is acidic, mixing it with new tap water may prevent some pH shock. For a pacu, though, I’d be inclined to use 100-percent new water in the aquarium. The fish will be better off for it. Good luck with your move.

Article Categories:
Fish · Health and Care