Money. I own 250 gallons , 125 salt and 125 fresh, without being rich.those tanks are expensive to maintain and the stocking isn’t the cheapest aswell.but most of it is used.point being you can maintain bigger tanks than your wallet „should“ allow with patience.what does a tank like this cost? 10 grand? Doable even without being rich.
The ones I've seen in videos for like the "mermaid show" tanks just continuously pump air. At a quick glance, it looks like you need a special kind of low pressure air compressor and a long tube basically, though most of the equipment is built for deeper situations than an aquarium. Systems for shallower diving look like they're somewhere in the range of $500-$1k? I don't know what it costs to refill scuba stuff or get certified, but you might end up simpler and cheaper in the long run by pumping air down there. I'd have to do more research though, definitely not something you'd want to screw up and find out the hard way that you're doing it wrong.
A bigger tank also gives more room to understock and just let the tank maintain water parameters on its own. But most people don’t want to look at an overgrown jungle I guess.
A demand valve is driven by you inhaling, when you stop inhaling the flow stops.
I'm pretty sure a valve forcing air into your lungs would not be a good idea to be honest, seems good way to actually blow your lungs out.
but the pressure directly behind the demand valve is being matched to the pressure where you are. this doesn't force air into your lungs because the pressure on the outside of your chest matches the pressure in the air in front of your mouth.
this is why you use your air faster on a deeper dive, and why you get oxygen toxicity if you go too deep without special air mixtures
Yeah you're totally right. I had misunderstood how the action of the demand valve worked. Commented further down this thread on my mistake. Owe that to you also.
You misunderstand how air supply underwater works, but that's cool... I got a minute.
Whether using surface supplied air or SCUBA, air needs to be compressed beyond surface pressures to be delivered to the diver.
Scuba equipment includes 3 critical components, (1) High pressure tank, (2) balanced first stage, (3) second stage / including mouth piece. If pictures help, click the links.
The high pressure tank supplies air at very high pressure... starting ~3000psi, which is too high to breath straight.
The SCUBA first stage uses an ambient pressure diaphragm to reduce tank pressure to a more manageable 120-150psi, and delivers the intermediate pressure to the second stage. more 1st stage details
The second stage provides the final adjustment to provide air at the pressure required for you to breath without struggling. Another ambient pressure diaphragm combined with a breathing resistance adjustment lever/knob sets the final air delivery within a range of slight positive to slightly negative. more 2nd stage details
Your body can only breath air at depth because the SCUBA system starts at higher pressures and uses ambient pressure diaphragms to step down the pressure to ambient at the current depth so that your own diaphragm can expand your lungs (or have air pushed in, if you set the regulator for positive pressure).
As a basic concept of the pressure of water and it's challenges, your torso is likely has more than 5 ft2 or 720 in2 of surface area. At 3 feet of depth, the water column already applies 1.3 psi on an object. This is a simplified view, but the math clearly gets brutal. A long 'breather tube' as suggested above would simply not work without forcing continuous air or using a regulator with an intermediate pressure described in in point #2 above.
The 'demand valve' you mention, is a term used for the second stage regulator valve, which would fail to operate without the intermediate pressure hose providing a sufficient pressure to operate the whole mechanism.
Yknow what I was just coming on to say your right I looked it up further and had misunderstood how that worked. I am wrong. So I downvoted myself, (didn't know you could do that either)
:)
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u/dzlux Aug 18 '22
CO2 in the tube is less a problem than the pressure difference. 2-3 feet below the surface and you will struggle to inhale without forced air.