Pump for bladder system

I have been trying to find bidirectional water pumps, does this one look like it would work? the only other ones I have seen are peristaltic pumps buit they are rather slow. or should i just get a pair of diaphram pumps? one for in and one for out.

https://www.aliexpress.com/item/1005004264135231.html

found another one that might work.

https://www.ebay.co.uk/itm/314508591141

the pump from Ebay is geared pump and in my experience they do not hold the pressure and you lose ballast over time.
On my first try i pinched the hose with a servo to prevent the bladder from empting itself.

There are some powerful peristalic pumps but you need some space for them.

The Grothen G1128 does 700ml/min:  https://www.aliexpress.com/item/1005004028135569.html

i couldn't find any dimesions for it, only for the G28 model which provides 500ml /min : https://de.aliexpress.com/item/1005004524631196.html

i agree with maxx78 on both counts:

1) geared pump == bad, peristaltic == good
2) flow means everything, and you want something that will fill the bag in 20 seconds or less.

but i will add these:
3) most of the 400 size motor pumps (motor is 28mm or so in diameter) are too small to be effective
4) if the seller doesn't post a flow rate, it is not worth looking at
5) if you don't find a pump that will fill fast enough, use more volts. (buy the 12v model, run it at 24v)
6) good peristaltic pumps aren't cheap

i just got one of these:
https://www.ebay.com/itm/284844980346
this is just an example, although this seller is in america, they come from china, so you should be able to find an international seller.

this one looks like it might tick all the boxes

https://www.aliexpress.com/item/32817707131.html

I agree with you on that pump, one recommendation, use the "Pharmed BPT tube" version. that tubing lasts longer and is more flexible than the silicon tubing.