i have a ipad thats about 6 yrs old. ive noticed that some of my apps keep taking more and more memory. freshly installed my prime video app uses 106mb. over time it grows to over 1.5gb. any way to stop this?

Either quit the app in the iOS background app switcher

AND/OR

In Settings app, under General, toggle OFF Background App Refresh.

If you would like to better optimise that iPad,

Tap on the link below to my iDevice/iOS performance/optimisation user tips link.

Slow iPad on iOS 9, 10 or 11! - Apple Community

Try all of these tips and leave each tip active together. Do not simply try every tip individually, expecting just one tip to be a performance “cure all”.

Many of these tips are designed to work together to help improve overall iOS/iDevice performance.

Good Luck!

The iOS App Switcher is accessed by double-clicking the Home button.

You'll see a series of application windows.

To quit an app, put a finger on an app window and hold and slide ypur finger upwards to quit the app.

To quit multiple apps, you can put a finger on each app and hold and slide your fingers upward.

Everything else I posted should be fairly self explanatory.

16GB iPad (or free remaining storage space) is not good enough for watching videos. Most apps (Amazon prime video, Facebook, email etc) will consume storage space as time goes by. You can't stop it. If you keep using the apps, they will consume more storage space.

ShagCA is correct.

A 16 GBs iDevice only has an effective storage space between 9-11 GBs at the most.

So, maintaining a usuable amount of internal free data storage space will always be a challenge.

This is why Apple quietly and with no fanfare or announcements did away with all 16 GBs iDevices in a, sort of, silent admission that 16 GBs iDevices offered little in the way of usuable data storage.

In addition, if you want to try and free up more storage space on your iPad.

You need to start by backing up your iPad to either Apple's iCloud or by connecting your iDevice to a computer running the latest iTunes or some other offsite, “cloud” data storage service, like Google Drive/Photos, DropBox, Box, etc.

Once your data is backed up,

Then delete any installed apps that you no longer use or use infrequently enough that they aren't missed (you can always reinstalled any purchased or free apps at some time later, as you need them).

Thin out/delete any music/videos/movies/TV shows/images/eBooks/eMagazine/iBooks/audio books/Documents/PDFs, etc.

If you use a POP email account on your iPad, delete/thin out any old saved emails that maybe saved to your iPad.

To permanently delete photos/images off of your iDevice go into the Photos app and find the Recently Deleted folder/album and permanently delete any photos/images stored in that folder/album.

Also, you can check to see what stuff is eating up all your valuable data storage space by going into the Settings App,,General Settings Panel, in the right hand column, tap Storage & iCloud usage panel ( in iOS 11, it’s iPad Storage ), in the top Storage Panel, tap the Manage Storage panel, wait for a list of apps to generate that will tell you how much space each app is taking up on your iDevice.

Then, do a hard reset of your iPad by holding down both the Home and sleep/wake buttons simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.

iDevices need to constantly maintain, at the very least, a minimum of between 2-3 GBs of free data storage space, at all times, to insure normal/nominal functionalities/operation and general overall performance of any iDevice.

Good Luck to You!