Your mediation settings tell AdMob how to choose between the AdMob Network, third-party ad networks, and house ad campaigns. The eCPM value determines the order of the ad network to serve ads, with the highest eCPM value served first. That means, if AdMob network or another ad network has a higher eCPM value with 100% or close to 100% fill rate, then the other ad sources including house ad campaigns will be served less often.
If you want to serve more house ad impressions to your house ad campaigns, try the following workaround:
- Set up an eCPM Floor for AdMob network with a reasonably high eCPM value.
- Set up a house ad campaign with the second highest eCPM value.
- Set the AdMob network eCPM value with the next highest eCPM value.
What this accomplishes is that AdMob network will first serve only ads that pay at least the eCPM floor value. Over time, this set up will maintain or increase AdMob network's eCPM value while the fill rate is likely to decrease, allowing the next ad source in mediation (in this case, house ad campaigns) to serve ads.