This is a good idea. Even if your current landlord was Ok with your 20g, it would have been prudent to mention your upgrade plans. You did add a sump and a bit more complexity to your system. As a non-hobbyist the setup, however simple you might think it is can appear overwhelming.
Yah I would consider it to be my fault too to some extend. I have to clear everything up with the new landlord I will be having.
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You wouldn't want to see my tank. I don't use fancy equipment and I am a noob