Imo your tank was over stocked when you bought the pacus. When I worked in a lfs I took care of trade-ins, most common were pacus over 15" and oscars over a foot. Rtc's over a foot were common too. Throw in those three plus your 18" potential pleco and the jd that tank is way beyond capacity. Your water is very cloudy even with all that filtration. I'll get off my soap box now.