Venturi for livewells

Guys,

I've been looking over the various designs and livewells projects here and theres some great work bye you guys, which helps others plan theirs, so thanks heaps in advance.

Something I have seen in my travells, over the years, is pro lobster fishers keeping crays alive in pretty warm water and warm air temp conditions out at the Abrolhos islands in plastic tubs on deck with water circulating systems.

Basically these are just the same as your own livewells.

However...one thing these guys do, which as yet I haven't seen done in any livewells, is aerate their water via venturi pipe (the bernouli effect) on the inlet water. (Just like a compressed air spray gun "sucks fluid up the pipe from the paint pot, just in reverse, this one sucks air downward thru the straw pipe and mixes it with the water!).

Where the plumbing pipe from the bilge pump is supplying water to the bottom of the livewell, they install a small straw like plastic tube into the top of the pipe (bottom cut on a 45 degree which protrues inside the pipe) - and it stands fixed to the side of the tub (read livewell) so that the top is just a little ( 1 inch)higher than the livewell level.

As the waters pumped thru the pipe bye the bilge pump, it sucks in air thru the strawlike tube - therebye aerating the water as it enters the tub (livewell).

This obviates the need for "pinhole sprays of water jet" etc around the top of the well via additional plumbing as well as obviating the need for 12v aquarium pumps & aerator stones and so on which only help to deplete your electrical supply quicker.

It's easy cheap and effective - hope it helps some.

Another thing to consider, with your livewells is that it's probably not a BAD idea, to have the drain outlet at the BOTTOM of the well - (at the opposite end to the now venturi fitted inlet), as this helps to "extract" the nitrates (read bream crap/shyte) that bream can excrete when under stress in a livewell environment....since it settles to the bottom!.

Should you elect to install a thru hull fitting below waterline in your hull for the inlet or outlet of your well - rather than pumping it both in and out over the transom, or out thru the hull above waterline - I strongly suggest that all such thru hulls below waterline should be fitted with a brass or stainless seacock, so that in the event of a hose failure - you can turn the sea DohDohDohDoh off to stop the boat sinking!

Again if you have ANY below waterline thru hulls, the hoses should be connected to the seacocks (which are fitted direct to the thru hull) with TWO stainless 316 hose clamps (not one!).

As a last resort - carry a few round tapered wooden dowels that can be hammered into a broken thru hull in the event one does break - at the thru hull / seacock joint...

Lastly - if you elect to install any thru hulls below waterline try and avoid like the plague the white plastic variety which have a habit of going brittle after a couple years and breaking.

The white plastic type are OK above waterline if you wish to save a few bucks...below water try and use either bronze or 316 stainless for those of you with alloy hulls.

One more thing - if your installing / building a livewell is to consider avoiding "square" corners, and acute angle corners (like you get with a diagonal seperator). While these might be OK for bream - often if you wan't to use that well as a livewell for small bait, they will swim up into the corner, get stuck there and die. Small baifish like that need to keep their head into the current, (to keep waterflow over the gills) so you want round (coved) corners in your well and a good water flow rate (like a 500 gph bilge pump).

Be sure to add a strainer to the outlet so baitfish, scales and other crap don't get sucked into it and block it ( leaving the inlet pump flooding your boat!).

Another "trick" worth considering (and I don't know the bream tournament rules on this - so maybe someone can comment) - IF you get a highly strung out fish (and it mightn't be a bream - lets say you have a trout - mulloway or some other species, even saltwater, that just won't settle in the livewell and is doing itself harm as well as the other fish therein)....you can quieten them all considerably with the judicious application of just ONE drop of clove oil from a small bottle with an eye dropper.

Clove oil is something you should be able to get from a pharmacist for toothache, it's a natural substance thats a great local anaesthetic (for a toothache) or for fish in a confined water volume situation like a livewell. (No using it to stun wildfish in waterholes - thats illegal).

As soon as you replace the water or release the fish into clean new water, they will recover very very quickly...

Like I said, only to be used where absolutely necessary and better check rules first - maybe it's not needed with bream (and I doubt it is, as they don't seem to be a very excitable species).

One last one is for warm water / tropics use, (or VERY hot summer days / heatwave type 40*C plus on the Swan) where water holds little dissolved oxygen, is to have a very small Oxy bottle from a oxy viva type setup - connected to an aerator stone via a low pressure adjustable regulator and allow a small tricke of pure oxygen into the water - that will stop any fish dieing on you. Of course compressed Oxygen needs to be treated with extreme care especially in case of a fire (you all carry fire extinguishers onboard?)

Air is only about a third (from memory) oxygen, and warnm water doesnt hold a LOT of dissolved oxygen at the best of times, aerating warm water doesn't actually raise the oxygen level very much..whereas pure oxygen does elvate it a great deal bye comparison making it much easier for the fish to breath thru their gills.

Hope this gives some food for thought for those designing / building new bream / bass boats and livewells etc..

Cheers!

[Geoff R]

Seriously you always are full of relevent info Trouty, top marks, however i got lost I don't spose you can post some pics or a drawing or something
Regards Geoff

[Geoff R]

Look at the pictures
I may not be very smart, but i "used" to be able to lift heavy things
Geoff

[Mick]

The "Keep Alive" brand of aerator uses the concept that you describe, they have a plastic tube with a valve on the end so you can adjust the flow of air and thus the size of the bubbles delivered. They are used by a heap of guys over here on the east coast.

[Geoff R]

But lets say for instance you catch a fish in fresh or brackish water and then travel to the weigh-in in salt, you let go a fish who may not be ready for the sudden change to salt.
I like a system that constantly turns water over so you don't have to worry about stuff like that, or can you incorparate both?

[jimi]

Geoff, I think this explains what trouty is on about

[Geoff R]

I think i get the idea now, so the water pumping through the pipe creates a vacuum from which air sucks down and mixes with the water. I might include this system in my next refit, what sort of tube dimension are we looking at and how do you insert it

[Bear]

No offence guys, but if you have a system that replaces the water, why then add extra as an aerator. The reason I have mine set up the way they are is that the turn over of water replenishes any oxygen loss and exposes the fish to the different water types.

I would have thought the less gear the better. If you are stuck with a system where filling or replacing the water is harder, then you will have to oxygenate of course.

JMO.

[Geoff R]

I just figures out how to do it myself, retic spray fittings would screw into the inflow pipe

[Geoff R]

Creating the best possible chance of releasing a fish in it's best condition possible.

[jimi]

Bear, I guess it depends on how often you run your pumps to replace the water. Maximising the amount of air in the water can only be a good thing if the pumps are spending some time turned off.

This system is about as simple as it gets. Lots of guys use the spray bars, but they can get clogged easily from any crap in the water. This system is much harder to clogg.

Geoff, those 4mm risers than you can get for retic systems would probably do the job well. Good thinking.

cheers
James

[Bear]

One of the reasons I did my live wells the y they are was after a chat with a guy I know in the East. One of the things talked about was stressing the fish. One thing brought up was that things like spray bars actually make a lot of noise and can cause a lot of water movement.

His concern was that he had no way to know how much that may have actually stressed the fish. I agree the aerator stone idea is a lot less agressive and wonder if one of the aerator bars you can get with fish tanks would suit more for the size of wells we use.

[Geoff R]

I remember scooping hordes of DohDohDohDoh out the bottom of my wells, after the fish was released, this system would prevent sediment on the bottom of the tank and totally turn the water over

[jimi]

Geoff, I'm not sure if that is good or not. If all that crap is blown around the tank it may end up getting into the fishes gills and eyes etc. and doing some damage. Might have to move the inlet slightly off the bottom to avoid that.

[Geoff R]

I wish Trouty was on he'd know exactly how to square this away