I wanted to—in my usual overly explanatory way, give some insight that might help in choosing a system that works for your needs and some of the science behind it all so you can be a better bait-keeper overall.
It may be quite basic, but beginning at the beginning is usually the best place to start. No matter what type of live bait you use in your area, they all use oxygen. But at the same time fish give off two other things that can reduce the time the bait will live. First is carbon dioxide. It seems simple to think that ‘if it breathes oxygen, then it gives off CO2’. But that’s not exactly true. In more truth, if it breathes oxygen, and has muscles, it then it gives off CO2. That sounds stupid, but it’s closer to the truth. Muscles use and burn the oxygen in the blood stream and as this energy is burned, the left over product is carbon dioxide. It moves back through the blood stream, to the lungs (or gills) and is expelled. The second thing that our bait exudes is ammonia. Actually, they also give off nitrites as well, but its not as critical as the ammonia. Ammonia is produced when an animal consumes protein. Our bait’s diet is nearly all protein, so they absolutely give off ammonia as part of their normal cycle. It sounds silly, but it’s sort of like fish pee. And when a fish is frightened, he may pee on himself. Some fish are thought to excrete high levels of ammonia as a defense measure. The ammonia has a terrible ‘smell’ to predators so like a squid using an ink cloud, if a minnow 'pees' in the water, it can give him a pee-cloud to disappear behind. It's not really pee, but that's the easiest way to draw that mental picture.
Enough about fish pee. The reason these things are important are that we now know we not only have to add oxygen to our bait, but we need to remove CO2 and ammonia and nitrites.
Let me just go ahead and say it, a Flo-Troll or other floating bucket is far and a way the simplest way to keep these chemicals in good balance. The issue with this system is two-fold. Its only about a cubic foot of area in which to keep bait, and it is difficult to navigate a kayak while dragging a bucket overboard.
In order to keep our bait really lively in a closed system like a baitwell or bucket, we need to manage those chemicals in the water.
Here’s some of the science to doing that.
I won’t go deeply into Henry’s Law, the work done by Boltzman or Maxwell or other formulas concerning barometric pressure or partial pressures or solubility. Let’s just consider the only thing we can actually control that affects dissolved oxygen in our bucket—temperature. Without discussing that warmer water affects hydrogen bonds with oxygen and forming ‘cages’ and whatnot, lets just be pleased to know that cooler water is capable of holding more oxygen than warm water. And very warm water can be nearly void of oxygen.
Keep your bait water cool whenever you can.
So how do we get oxygen into the water? A two minute chemistry lesson teaches us that oxygen diffuses into water in three ways—by plant photosynthesis, by diffusion at the surface and by diffusion from aeration.
We know what photosynthesis is, what the heck is diffusion? Diffusion is basically the spreading out of something. In our case, it’s moving oxygen from a higher concentration to a lower one, in layman’s terms.
We are keeping bait water in a bucket, so photosynthesis is out. That leaves diffusion. A lot of folks think the bubbles from an air pump is putting oxygen into water. Actually, only a tiny amount of oxygen is being diffused into the water.
In order for diffusion to take place, it takes surface area--a lot of area where air and water are touching each other. A bubble really doesn’t have a lot of surface area. Even a thousand little bubbles don’t have a lot of surface area. The largest surface area for our oxygen to diffuse is on the surface of our bucket. No, I’m not saying that just having a surface area of water in the bucket is going to be enough to keep the minnows alive. The process of diffusion takes a lot of time, unless it has some help. Agitating the surface of the water will speed up this process. It does two things, it actually increases surface area and it moves water of high oxygen content away, and water of lower oxygen content into play.
If you let a bucket of water just sit still for a long time, there will be more oxygen in the water at the top of the bucket than at the bottom. This is where the diffusion has taken place--right at the surface where the air and water are touching each other. The diffusion will continue until the water at the surface has reached its saturation level—meaning it has all the oxygen it can carry, with a given set of chemical parameters like altitude, barometric pressure and such. The key is to get that already saturated water away and move the least saturated water up to the surface where it can soak up that oxygen at the surface. Yes, we need to circulate the water. From bottom to top, preferably. This also brings into play the other chemical we can and need to control in our bait bucket—carbon dioxide. Just as diffusion works to add oxygen to our water, it works in reverse to remove the high levels of CO2 from our bait water. Another very important reason to circulate the water.
Before we talk about how to circulate, I would like you to think about a fish tank you’ve seen in a dentist’s office, office building or a friend has. Specifically, a high-end aquarium system like a reef tank or other delicate salt water tank. Have you ever noticed these tanks typically have no air bubbler? Look closely at these systems and you’ll see that what they do have is a couple of high pressure water streams circulating the water at the surface rapidly, and circulating the water in the tank. That’s right, they depend solely on surface diffusion to put oxygen into the tank.
Whether it’s a pickle bucket, a cat food container, a 300 dollar livewell or a 25qt cooler, you should understand by now that keeping the water circulating is the most important thing. Of course the most effective way is in a water replenishment system, one that uses a livewell pump and just circulates fresh water into the tank, and removes the old water out. This system also removes that third chemical that we cannot control in our bucket system—ammonia.
The main drawbacks from this type of system is not only cost—which could be hundreds of dollars, but also space and portability are issues. I would also remind folks that even a very small baitwell pump will draw 2 amps. Unless you are considering a full sized marine battery, you may only get 3 or 4 hours of use from the system. After that, your bait can go tits up pretty quick.
For ease on the wallet and portability, if we choose the bucket option we can still choose many different ways to circulate the water to increase our diffusion. Again, the livewell or bilge pump is an awesome way to circulate the water but the battery life can be a restriction.
A very simple, cheap and extraordinarily portable solution is the 15 dollar bubbler. They do a very good job of circulating the water from bottom to top, as long as the batteries are strong and the bubbles are moving the water at a good rate. Don’t be lulled into thinking that the ‘bubbles’ are the main factor putting the oxygen into the water. Hopefully I conveyed that fact, but I’d be a liar if I said that ‘no’ oxygen was being diffused into the water directly from the bubbles. It’d take some higher math than I’m in the mood for to come up with what is actually being put into the water from the bubbles, but from what I could guess I’d say about 1/10th of the oxygen being diffused into the water is from the bubbles. The other 90% is from the bubbles causing circulation of the water and thereby helping with the surface diffusion.
Keep the batteries strong to keep the flow strong, and make sure the air stone is on the bottom of the bucket or cooler. This will aid in moving the less oxygenated water at the bottom, moving toward the top.
What about those sprayer type gadgets? Man, just think about what those things do. It's bait well magic. They circulate water from the bottom to the top, they spray water on the surface with great pressure creating a huge amount of surface area for diffusion and this turbulence also produces bubbles which has 'some' benefit. These are the Holy Grail of a closed system. BUT--they are again a 12v system and can be limited on the number of hours they will operate at full capacity.
The ammonia build up in a closed system is something to consider. There are a few ways to reduce the build up including removing any dead baits.
Here’s a factoid. It is a common ‘fact’ that a dead fish uses 10X more oxygen than a live one. The additional oxygen is burned by bacteria growing on the decaying fish. This fish also gives off an enormous level of nitrites, which ‘foul’ the water. Get those dead baits out.
Using a bait tank that has rounded sides will not only keep the fish swimming in a natural way and reducing physical damage but will also keep them from stressing out when they get stuck in a ‘corner’ and release ammonia during this stress.
Keeping the tank dark will also reduce stress. A dark colored bucket, with a dark lid will reduce this stress.
It’s also recommended to change out at least a third of the water in a closed system, every so often. Every hour or so, I think is sufficient. If you see foam on the surface or your baits are gulping at the surface, a drastic water change might be in order.
Over crowding a bait tank is a real issue, whether it’s a closed system or a circulating system. While it’s impossible to really predict how many baits your system will hold, I can give you this bit of information, if your bait tank is capable of surviving say 35 baits of a given size, if you put 40 baits in there, in spite of what you might think, 5 of them won’t die—all of them will. The stress of over crowding will be spread over all the baits, not just the unlucky few. If you experience what you believe as an overcrowding issue, take out MORE baits than you think you have to. The extra room and better chemical exchange will hopefully bring the rest back to a useable state. Better to lose a third of your baits by removing them, than to lose them all and ruin a day on the water.
An insight on what we use in our fishing, I actually have a couple of each type. I have buckets with bubblers, a Hobie self contained lifewell, a large capacity recirculating custom system and a couple of Flo-Troll buckets. Each has it’s use, each has it’s pros and cons.