My tinny has transom platforms and on one I have a 20lt bucket secured. About 200mm up I have fitted an elbow through deck fitting to the bucket from which I have enough hose to submerge a bilge pump thats fitted to the end. I can swing the pump up when not in use and being 200mm up, when the bilge isnt on the water drains but leaves some in there. Extend the wiring from the bilge and fit aligator clips so you can easily connect to a battery. The bucket was for trans fluid and the lid has a pull out pour spout. With lid on and pump going, fresh water circulates and exists from the spout, spilling back in the water. For small bait fish you could fit a stocking so no fish get flushed out. The bucket gets used for a range of things other than keeping bait live. I catch squid and put them in there with lid on and every now and then wack the bucket so the squid spook and ink and out comes the inky water, I hate burst ink sacks so this way the squid gets rid of their ink first. If your tinny doesnt have transom platforms Im sure it isnt guna be hard to secure or hang a bucket off the back. Works for me and was quick and cheap to make. I can post a pic if you need, cheers.

On my old tinnie(that my brother now owns in katherine NT) i used to use one of those 20L drums with the big screw on lids that you can get from any outdoor store and put it at the rear of the tinnie near the fuel tank. Good that it offset the 20L of fuel on the other side of the rear.

Like these

http://www.plasticsplus.com.au/products/large/018.jpg

Never got around to putting a bilge pump setup in it. Just used to pour some water out and new waterback in everynow and then with a smaller hand pale. This worked well for live Cherabin, lasting from dawn till dusk. To tell the truth one day we had 20 in there and it took 2.5 hours to drive down stream to our fishing spot and didnt change the water the whole time. All the Cherabin were alive by the time we got there, and we fished for about the next 3 hours till they ran out, but still didnt change the water.

Though i am guessing Cherabin dont need as highly oxygenated water as say live fish/mullet would.

i can send u some pics of my tinnie and live tank and eskie if u like, or u can pop over and have a look your self,  mine has water going though it when evea it is on so the live bait stays nice and fresh

cheers andy

is a good size bucket for life bait. Problem with life bait tanks is often temperature rather than Oxygen. I find if the tank doesnt heat up the bait will survive with an airator. However up here in summer the water gets hot in the tank, and that kills the bait, hence you need flow, or replace water often. My tank in the tub is built in, has an overflow, so I simple pump fresh water in, let the overflow drain it, and use an airator.

I have a cheap eski that hold about 35 liters of water and a bilge pump with a length of hose and some T-pieces with drilled out nozzels the pump recircs the water putting oxy back into it  , it works of alligator clips so you can put it in the boat or leave it at home as you need it and take it out to use on the bank at night if you want .makes for easy cleaning too and the insulation helps keep the water cool on those hot barra catching days .