I did a Google image search of gravel cleaner.

There is one which sounds something like that one with an airline exit and I can't find where it was listed. But it suggested that the product would not pull the gravel up and out of the tank. That sounds good but I got the impression that the exit hose was so small that gravel couldn't get through it, though it could probably do a pretty good job of clogging up.

Through presumably good intentions (keeping the gravel in the tank) the thing has got to be incredibly inefficient. That would be sort of like limiting pollution by putting a small lawn mower engine in a car! :)

http://www.first-choice-aquatics.co.uk/acatalog/info%5f7292%2ehtml
catalog has a product which would not be my first choice for a gravel cleaner. It would not even be my last choice. You can imagine what choice the company might be.

"They" designed a gravel cleaner to re-channel all of the dirt through a power filter. This way all ammonia, nitrite and nitrate and any other toxin such as hydrogen sulfate (which produces that rotten egg smell) will be drawn out of the gravel and sped past the fish's gills!

Supposedly the water is channeled through a filter with a "an efficient replaceable filter bag" with "micro-porous material to trap even the smallest of particles". So the aquarist is supposed to buy a filter,  replaceable bags and a gravel vacuum so they can "save water". While the thought is awfully gross, I can just see them trying that with similar efficiency on a full toilet!

I don't imagine that they achieve the level of dialysis, which is what they would about have to do to leave a safe fish tank. Can you imagine the expense of running a dialysis machine on an aquarium?

They have a battery version of this so you can spend money on batteries while poisoning your fish.

Decades ago "they" had a hand pump which sucked the water out of the tank, through a fiber bag and back into the aquarium. I think I got it with a bunch of gear stuck in a used aquarium. After a couple of messy tries, where the water and fine dirt really roiled that aquarium while pouring through the bag, that clunker was tossed. Wish we had today's recycle barrels. It would have been there in a heartbeat!

For small aquariums I do have a small diameter hose (about 1/4 inch/ .63cm interior diameter) running from the larger (1.5 inch/ 3.81cm interior diameter) tube. Somewhere there is an even smaller one of those designed by guppygirl several years ago. It could actually clean tiny, tiny containers like a gallon fish bowl or a shoebox. But usually one wants a larger diameter gravel vacuum.

My python water changer's line has an external diameter of 5/8 inch or about .6cm. A similar gravel vacuum has an interior diameter of 1/5 inch or  1.27 cm. The larger tube has an exterior diameter of 2 inches and and interior diameter of 1 and 7/8s inches or 5.08 & 4.76 cm. Those get a jib done pretty fast.

If your gravel vacuum actually has an exit tube as small as airline tubing and you need to replace it or pull it off and even cut the clogged section off (quite likely as it gets clogged) put the end of the air tube under hot water and it should become malleable enough to get it onto the adapter connecting it with the slightly larger "vacuum" tube.

If you can knock the gravel out of the thing, I would seriously consider returning it to the shop and asking if I could get a refund or if I could trade up to a use-able gravel vacuum.

As for glue guns, I do think we have have talked about using them several times on Guppylog. That is what doing a Google search of Guppylog would suggest. And in certain cases it might work if allowed to completely dry and have any fumes vented.

That glue from the glue gun is meant for things which will not flex. Wouldn't it break its seal in the process of gravel vacuuming?

Also the glue may not be "food quality".

There are other kinds of more expensive air lines. I picked up some of that green silicon tubing. It is useful in places where the airline needs to be bent and twisted in tight corners. And it doesn't fry out anywhere near as fast as regular airline tubing. It does more easily attached to filters and hard airline tubing. But it has an unfortunate tendency to crimp shut and so isn't used a lot here.

While visiting killie people in Phoenix, AZ a couple of months ago, I picked up some used black airline tubing at the tail-end of an auction. It is supposed to be superior to the regular stuff and I thought that it might come in handy as the air system here is extended. (It also packed around a small styro of fish in my suitcase.) Unfortunately the guy selling it had so conscientiously taped it together so completely that it was all sticky when the tape was removed. Before leaving for the AKA convention three days ago, I slid all 100 feet of that sticky black tubing into a 40 gallon bleach solution. When we are completely unpacked from that nearby Milwaukee killifish show and too many new fish are given homes here or given to friends tomorrow or the day after, I'll have to check that black tubing.

If you were sold a gravel vacuum with a tiny exit hose, in the name of a lesser price or the ability to prevent gravel from getting drawn out of the aquarium, I would replace that inefficient clunker with something which might work.

A little gravel will wash out. That is why an aquarist should use a bucket for waste water. When I had one tank, the bucket was one also used for washing floors and doing other chores. Any gravel washed into it was tossed in the garbage, into the gravel driveway or put under a sagging patio stone. (The decorative garden gets the dirty but not toxic wastewater.)

One should hold a finger not too far from the end of the gravel vacuum. If gravel starts to move way up the larger tube, the finger is quickly placed over the outlet. That stops the flow of water without breaking the siphon. Hopefully the gravel will recede back into the tank. Though it can be a little messy, you may have to raise the tube a bit so that gravel can flow into the aquarium.

I've even been clumsy enough to let fry into the larger tube. Sigh. Then one has no choice but to raise the tube off of the tank bottom. If the fry don't get the idea that they should swim down and out, gently raise the small tube and let some water flow back into the aquarium. If that doesn't work, all of the water in the gravel vac may have to be allowed to wash back into the aquarium. One goes and answers e-mail, does homework or grades papers or run errands while the dust settles in the tank.

For those who go to the trouble and expense of buying two buckets dedicated to aquarium care, an "in" bucket (also good for seasoning new water) and an "out" bucket may have at least one other option. I periodically bleach and dechlorinate the out buckets. If that bucket is relatively clean and bleach free, a fry can be allowed to wash in there and just be netted or (usually here) scooped out with a hand.

Judging by the time, I'll get to the fish tomorrow morning. They are separately and properly bagged and in a closed fish shipping box. It is dark but warm enough in there. They should remain inactive and safe until then.

Afterwards I'll check back in on your situation, tomorrow afternoon at best I'm afraid. :)