Pony tank

[Coztick]

Primary Gas = (back mounted cylinders, or side slung cylinder(s)) gas used during the dive. Part of the gas calculation.

This is where my application of a "pony" gets vague.
I consider it my left cylinder while diving a single 80s on recreational, tropical dives.
I don't see the need for 2 80s but I'm not willing to give up redundancy.
The smaller cylinder is my designated emergency gas and yours is maintained in the larger cylinder with the long hose.
Without an emergency, it is never consumed.
I do use it to ascend on the last dive of trips and haven't needed half of its capacity.
FWIW I have surfaced with plenty who have nearly drained their only cylinder...

 

[Gareth J]

This is where my application of a "pony" gets vague.
I consider it my left cylinder while diving a single 80s on recreational, tropical dives.
I don't see the need for 2 80s but I'm not willing to give up redundancy.
The smaller cylinder is my designated emergency gas and yours is maintained in the larger cylinder with the long hose.
Without an emergency, it is never consumed.
I do use it to ascend on the last dive of trips and haven't needed half of its capacity.
FWIW I have surfaced with plenty who have nearly drained their only cylinder...

Sorry for not being clear. A pony is a small cylinder (in the UK generally 3 litres), an addition to the primary cylinder. The primary cylinder carries the "dive" gas. The pony carries emergency gas, which is not, under normal circumstances used during the dive.
How the pony cylinder is carried varies, from side slung, too secured to the back mounted primary gas cylinder.

Personally, when diving single cylinder rigs, I always preferred my pony inverted and mounted to the side of my primary cylinder. I know many prefer to carry it as a side slung cylinder. Generally, pony cylinders are only carried by those diving single cylinder rigs. Ultimately it's about convenience and personal preference.

I hate carrying a side slung if I can avoid it. That said, I almost always have a Ali'80 side slung on my left side because I predominantly dive CCR. So, even if I am shallow enough not to require the side slung, I am carrying it for an OC buddy.

 

[Colliam7]

I typed in pony tank or pony bottle in the search bar and nothing came up.

I am not altogether surprised. Unfortunately, our Search function here on SB is not as 'robust' as we might prefer.

The majority of threads on the subject are posted in this subforum - Tanks, Valves and Bands - as well as in the 'Solo Divers' subforum.

Try this: type 'pony bottle' into the Search bar (without the quotation marks). If a menu pops up with check boxes such as 'Search titles only', or 'Posted by Member', or 'Newer Than' or 'Search this thread only' or 'Search this forum only', make sure you uncheck ALL of them. That way you don't restrict the search to any particular member, or forum.

You should get a list of ~101 posts to look at, in a variety of threads.

For bettter or worse, the discussion in this thread veered off a bit, in the direction of how to use (or how NOT to use) a pony bottle, rather than addressing your question, about what equipment options are available, and why one might be better or worse than another. That is both the good and bad of a social media forum like SB. You get mnore than you were expecting, whether it is always what you want or not.

 

[OTF]

The other way to search is entering something like

"pony bottle"+"scubaboard"

into google and make sure you click the "more results from scubaboard" link under the first couple of returns