How long is your UGF ?
In my 15gal with 20" long UGF Africana and Malaya last less than 8 months .Filter is Eheim 2213 + 2x Jagno. In other 2 15gal with 45" long UGF the same substrates are 14 months already and they will last 6 more at least. We need to have long pipes or very low water flow in order to keep ADA strong. My UGF is covered with 1.5" of Matrix ,Substrate is 2-2.5"