Livewell
How do you keep fish alive in a livewell all day?
Quick answer
Volume in gallons is length times width times depth in inches, divided by 231, and turning that volume over every 15 to 20 minutes keeps oxygen in the water without churning the fish. Warm water holds less dissolved oxygen than cold, so the hottest day of the season is the hardest day to keep fish alive, which is exactly when a recirculating kit beats pumping in more warm lake water.
A livewell that looks full and running is not the same as a livewell keeping fish alive, and the difference usually comes down to two things: whether the pump actually turns the water over often enough, and whether the water going in has any dissolved oxygen left to give. Both problems get worse as the day gets hotter, which is the opposite of when most anglers start paying attention to the livewell.
This guide covers the published math for how many gallons your well actually holds, the turnover convention that decides how it should be pumped, why the hottest day is the hardest one, and where a timer or a recirculating kit earns its keep over simply running a bigger pump continuously.
On this page
- How many gallons is your livewell, really
- How often should the water actually turn over
- The surprising math behind the turnover convention
- Why the pump on your boat is bigger than turnover alone requires
- Setting up a timer to hit the turnover convention
- The hottest day is the hardest day, not the calmest one
How many gallons is your livewell, really
Measure to the waterline you actually fill to, not the physical top of the well box. A well built to hold 30 gallons at a brim full fill might only be run at 20 gallons in practice to leave freeboard for fish movement, and the 20 gallon figure, not the 30, is the number every other calculation in this guide should use.
Livewell volume from measured dimensions
Published figuregallons = ( length in x width in x depth in ) / 231 Example, measured to the actual fill line: 24 in x 16 in x 15 in = 5,760 cubic inches 5,760 / 231 = 24.9 gallons
231 cubic inches per US gallon is a published constant. The depth you plug in is the depth you actually fill the well to on a normal day, not the depth of the box itself.
How often should the water actually turn over
Turning the entire volume of the well over every 15 to 20 minutes is the convention repeated across bass fishing and livewell equipment alike, and it is a convention rather than a published standard because no regulatory body sets it. The reasoning behind it is straightforward: enough turnover puts oxygen back into water the fish are consuming it from, without moving so much water so fast that the fish spend the day being tumbled by current inside a small tank.
The surprising math behind the turnover convention
Run the turnover requirement against a real livewell size and the required flow is far smaller than most stocked pumps actually deliver, which is not an error, it is the reason a timer exists at all.
A pump rated at 360 GPH satisfies the 15 minute turnover convention for any livewell up to about 90 gallons, which covers nearly every livewell on a fishing boat.
Rule of thumb Boating and fishing convention rather than a published standard. Taught everywhere, useful, and not a specification. Nothing enforces it and no body publishes it.
| Livewell volume | GPH needed for 15 minute turnover | Smallest stocked pump that covers it |
|---|---|---|
| 15 gallons | 60 GPH | 360 GPH |
| 25 gallons | 100 GPH | 360 GPH |
| 40 gallons | 160 GPH | 360 GPH |
| 60 gallons | 240 GPH | 360 GPH |
| 90 gallons | 360 GPH | 360 GPH |
The 15 minute turnover figure is convention, not a published standard, and the smallest pump commonly stocked already clears it for nearly every well size a fishing boat actually carries. Pumps rated well above 360 GPH exist to fill and drain the well quickly at the ramp, which is a different job than keeping already present water aerated.
Why the pump on your boat is bigger than turnover alone requires
A boat shipping with an Attwood Tsunami MK2 aerator pump T800, 800 GPH rated at 800 GPH is carrying roughly eight times the flow the turnover convention calls for on a typical 25 to 30 gallon well, run continuously that pump would turn the whole volume over in under three minutes rather than the recommended 15 to 20, which does nothing useful and simply tumbles the fish against the walls of the well all day. The 800 GPH figure exists because the same pump also has to fill and drain the well quickly at the ramp, a genuinely different job from ongoing aeration, and running it flat out for both jobs is where a livewell timer earns its place: it uses the pump's full flow in short bursts and lets the interval between bursts do the averaging down to the 15 to 20 minute convention instead.
Setting up a timer to hit the turnover convention
- Confirm your well volume at the actual fill line. Measure length, width and depth to the waterline you actually run, and calculate gallons using the formula above rather than any figure printed on the boat's own specifications, which usually describes the box at brim full.
- Install a timer inline with the existing pump wiring. A budget option like briidea livewell aerator timer with intelligent timing control or a tournament standard such as Flow-Rite Livewell Timer Pro wires between the switch panel and the pump, cycling it on and off rather than replacing the pump itself.
- Set the on interval short and the off interval to match your volume. Aim for the pump to move roughly your well's full volume across each on and off cycle combined, at the 15 to 20 minute turnover convention. A well that turns over in three minutes running continuously needs an off period several times longer than its on period to average out correctly.
- Shorten the interval on the hottest days. Warmer water holds less dissolved oxygen to begin with, so run the aggressive end of the turnover range, closer to 10 minutes, on the hottest days of the season rather than the gentler 20 minute setting that is fine on a cool morning.
The hottest day is the hardest day, not the calmest one
Warm water simply holds less dissolved oxygen than cold water, which means the day everyone is least worried about the livewell, a calm, sunny, hot afternoon, is exactly the day fish are hardest to keep alive in it. Pumping in more raw lake water does not fix this if the lake itself is the warm water the problem started with. A recirculating kit such as Attwood Tsunami MK2 Recirq aerator kit, 500 GPH solves a different problem: rather than continuously drawing in more of the same warm lake water, it recirculates the water already in the well through its own aerator spray head, which adds oxygen back into water that is already there and, because it is a smaller, self contained loop, tends to run cooler than a lake at full summer temperature. It is also the only configuration that keeps oxygenating the well while the boat is running and a thru-hull cannot be open.
Frequently asked questions
How do I calculate how many gallons my livewell holds?
Multiply length, width and depth in inches, measured to the waterline you actually fill to rather than the top of the box, then divide by 231, the published number of cubic inches in a US gallon. A well measuring 24 by 16 by 15 inches to its normal fill line works out to about 24.9 gallons, which is the figure to use for any pump sizing or turnover calculation rather than a number printed on the boat's own specification sheet.
Why does my boat come with an 800 GPH pump if turnover only needs a few hundred?
The same pump handles two different jobs: filling and draining the well quickly at the ramp, and keeping already present water aerated once the well is full. A high flow pump is sized for the first job. Running it continuously for the second job turns the well over far faster than the 15 to 20 minute convention calls for, which is why a timer that cycles the pump in short bursts is the correct fix rather than a smaller replacement pump.
Is the 15 to 20 minute turnover figure an official standard?
No, it is convention repeated across bass fishing and livewell equipment rather than a figure any regulatory body publishes. It reflects a practical balance: enough water movement to keep dissolved oxygen up without moving so much water so fast that fish spend the day being tumbled by current, and different anglers reasonably run slightly tighter or looser intervals depending on species and water temperature.
Why are fish harder to keep alive on hot days than cold ones?
Warm water holds less dissolved oxygen than cold water, so the same livewell setup that comfortably supports a limit of fish on a cool morning may be marginal for the same fish on a hot afternoon, even with identical turnover. This is also why a recirculating kit that keeps existing well water oxygenated, rather than continuously drawing in more warm lake water, becomes more valuable as the temperature climbs rather than less.
Should I use a recirculating kit instead of a straight thru-hull pump?
A recirculating kit solves a specific problem a straight thru-hull pump cannot: keeping the well aerated while the boat is underway, when a thru-hull intake may not be usable, and on hot days when the lake water coming in is itself the warm water causing the oxygen problem. Many anglers run both, using the thru-hull pump for quick fills at the ramp and the recirculating kit for aeration once the well is full and the boat is moving.
How do I know if my livewell is overcrowded?
Watch the fish rather than relying on a stocking number, since no published figure accounts for species, fish size, water temperature and how long fish will be held. Fish gulping repeatedly at the surface, lying on their sides, or losing color are signs the well is overloaded for current conditions, and the fix is fewer fish, a shorter turnover interval, or cooler recirculated water rather than pushing more warm lake water through a pump that is already running.
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Researched, not professional advice. This page is compiled from published engineering and regulatory figures, manufacturer specifications and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are boating convention rather than published standards, and they are labelled that way wherever they appear. Marine electrical work is not house wiring. Use tinned, finely stranded marine cable, size it for voltage drop and for the ABYC E-11 ampacity table rather than one or the other, and put overcurrent protection within seven inches of the battery positive terminal, because everything between the post and the fuse is unprotected. A lithium battery needs a charger with a lithium profile. Never load a boat past its capacity plate, and remember that canoes and kayaks carry no federal capacity plate at all, so their stated capacity is the manufacturer own figure. Wear the life jacket, and treat early season water as the hazard it is: cold water immersion takes your breath and then your hands long before it takes your core.