In January 2023 I cut a 275-gallon tote in half along the horizontal weld seam, plumbed the top half as a grow bed over the bottom half, and started running it as an aquaponic system in the corner of our back shop. Fourteen months later, I can give you a real report — not the cheerful brochure version.
The build in five sentences
Bottom half: fish tank, 135 gallons after allowing for the standpipe. Top half: media-filled grow bed with about 2.5 cubic feet of clay pebbles in a bell-siphon ebb-and-flow configuration. Recirculating pump at 450 gph, rated for continuous submerged duty. Heater: 300W with a thermostat set at 74°F. Lighting: ambient shop fluorescents plus one LED bar over the bed.
The biology timeline
- Week 1-4: cycling with pure ammonia addition, watching nitrate rise.
- Week 5: added 14 bluegill fingerlings and six tilapia.
- Month 2: first basil harvest, about 90 grams. Too early to really judge.
- Month 5: tilapia at about 8 oz each. Lost two bluegill to a temperature spike when the shop heater went out on a cold weekend.
- Month 7: pump failure at 3am on a Friday. I noticed by 9am. Lost one more tilapia and most of the basil. Added a cheap battery alarm on the pump outflow.
- Month 10: harvested first four tilapia. 1.3 lb average. System had fully stabilized.
- Month 14 (today): ongoing, eight tilapia, steady basil production, occasional chive and mint.
What the tote did right
The geometry of a 275 is weirdly perfect for aquaponics at the hobby scale. The bottom tank volume is enough for a small breeding population without needing industrial filtration. The top-bed volume matches the biofilter needs of the fish load, if you stock conservatively. And the cage — which I left on, except for two cross members I cut out to make room for the bed frame — is a ready-made support structure for a grow bed that wants to hold 250 pounds of wet media.
What the tote did wrong
HDPE bulges. Not dramatically, but under the weight of a fully flooded grow bed, the top half warps enough over months that you need to either add a lateral brace or accept that your bell siphon will need to be re-leveled every three months. I added a 2x4 brace in month 5.
A fish tank in an HDPE tote is not a decision, it is a relationship. The tote will move. Plan the plumbing to survive slow deformation.
Economics
Total out-of-pocket was modest — pump, heater, siphon parts, and clay media. The tote was shop-stock. Annual electricity ran about what you'd expect for a small recirculating setup. Fish produced in 14 months: about 14 pounds of tilapia. Basil: maybe 2 pounds dry equivalent. If you bought the fish and the basil at a grocery store, the grocery run would come in well below the build cost. So the economics are bad. The project is worth it for everything the economics don't capture.