Northwest Dive Club

So When you folks that have these pony tanks get them filled, do you have them checked each time you fill them?

Do you eventually empty the air and refill periodically? Is there any problem with leaving that air inside for months? I have never seen one used with a separate pressure gage, only with an octopus connected.

Is it prudent to leave the octopus on the main tank's first stage, and add an additional octopus to the pony tank?

Okay this is getting too complicated........ how about this. Tell me how YOU connect up the pony to YOUR ideal system.

A pony needs no octo. You can leave air in a pony a long long time.

A pony is simply a small (minimum 19cf) tank with a second and SPG so you can at least check tank pressure before the dive.

thats it.

Come to the ththth dive tonight, and I will show you!
My pony is attached to my main cylinder via a quick mount setup. It has an spg, and a regulator attached. I have it checked whenever the vip date expires. I have it topped off whenever it gets a bit low. I do not calculate the gas in it as part of my diveable gas supply, it is just for emergency use.

So you guys don't have The octopus on the main first stage tank, you put the octopus on your pony right?

That's how I'm doing it. I'm not setting it up as a solo diver configuration.

Given that a pony bottle may or may not be with you on each and every dive, it remains prudent to have both a primary and backup 2nd stage on your main tank.
I sling my pony the same way I would carry a deco or stage bottle. Same kit, same procedure for deployment.


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So you're diving with two octopus one on the main first stage and one on the pony bottle?

How big a Pony are you guys choosing? I think the 19 is the prudent size, for my needs thats 10 minutes plus or minus based on my proportional consuption with main tanks now. Ten minutes is enough to get somebody in heavy breathing panic mode to a safety stop and up to the surface. 13 might be 5-8 minutes?

What say you?

A first stage, primary second stage, bungied backup second stage, and SPG on back gas (main tank(s) on your back). A first stage, second stage, and SPG on any other breathing bottles.

Air can sit in a tank for a long time, but you should breath off of all of your regs on surface as part of your pre-dive check every time you dive.

As for size....what's your working SAC or RMV rate?

Look up "stage bottle rigging". Note that the second stage for the slung bottle remains bungied to the small tank, not attached to your body. And it's not called an octo. The advantage of this system is that it works for a range of tank sizes, all of which may be easily unclipped from your body and handed off to someone else. This is convenient for climbing up a ladder back onto a boat, as well as possibly transferring to another diver under water.

By the time you start carrying a pony, you need to educate yourself on the more common terms and procedures used for technical diving. A pony bottle isn't a huge deal, but it will pay to use it in a manner that is consistent with more advanced diving.


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Nothing says a pony has to be stage carried. It can be solid mounted to the main tank.

Although if you ever plan on going into technical diving, learning to stage carry now will be of benefit. Otherwise just go solid pony mount to main tank.

Here's my experience with pony's...

1. Observe unconscious diver on bottom
2. Approach diver and signal "brah, are you ok?"
3. If unresponsive, position yourself laying on top of unconscious diver
4. Let all the gas out of your wing
5. Secure unconscious divers reg in mouth, ensure open airway, start gently inflating unconscious diver's wing to lift both of you off the bottom and heading to the surface.....during which time you will be RIDING THE PONY! Yeeehaw!

Thanks for your comments in this. If the terms I've used here don't match the proper technical descriptions common in America. That is likely due to my learning scuba in another poor third world country.

One of the reasons I am part of this site is to get better acquainted the cold water systems, and obviously now to learn the proper terms when discussing such matters.

All you folks taking the time to provide comments on this are much appreciated!

I mount my pony to my main. It has a SPG on short hose I can read pre-dive but only a buddy can read during dive. I'm never in deco and I'm immediately going to 15 feet rest stop or the surface if I have to use my pony. Since I always breath the reg pre-dive and occasionally during rest stops it gets low. Instead of paying for fill or requesting top off I top it my self with a fill transfer. It gets complete refresh during VIP. I use a 19 cuft or 30 cuft depending on planned depth. I balance with 2 lb weight on opposite side in back.

The size of the tank used as a pony bottle depends on your air consumption rate (SAC or RMV) and your max depth. A 19 cuf tank is generally considered the smallest size for a slightly stressed consumption rate of 1 cuf/minute and a max depth of 100 ft. Given that it's best to check the tank with a couple breaths before each dive, a more practical size might be 30 cuf. I find the 30 size to be most comfortable to sling on my left side. I've also slung 40 cuf tanks as pony/stage bottles.
Once you get used to slinging a 40, then moving up to an Alu 72 or Alu 80 for more advanced dives is not a big deal.
A pony bottle is reserved for emergency use, though a little practice under water under non-stressed conditions is a good idea. Pony bottles are filled with air, so their max depth is not limited as it would be for Nitrox.
Considerations for using a pony bottle are covered in the Deep Diving specialty course offered by a few agencies.

If you can find them (I have several) luxfer made a tall 30cf tank that makes a perfect back mounted pony. They are tough to find though.

Although Personally speaking, I wouldnt have straight air in a pony, I'd have probably 30%, as even at 130ft, its just under 1.5PPO, and you can easily breath that if needed. If its a stress situation, abit extra O2 is always welcome.(and less nitrogen)