What is the purpose of the zeolite?
[0] Measure your tank water.
[1] You can measure the ammonia and nitrite in your output water, that is the water your pump is pumping out of your filter. If it has any readable ammonia (for ammonia test tube reference use the same test tube but of tap water or bottled water, not the paper color chart) or nitrite, then, yes, either reduce the bioload or increase the filtration and the turn over in the tank.
[2] Rule of thumb says no more fish than 1 cu inch of fish per gallon of water. A two-foot RTC's body volume is 2 feet (24 inches) x 3 inches (average width, from say 10" at cranial to 1/4 inch tail fin) x 6 inches (average height) = this comes to 432 cu inches, while your tank is 260 gal + 66 gal sump but neither is full to the brim, so overall volume is say 280 gal.
432 vs 280 - with one RTC you are already 1.5x over the limit.
Even if we guesstimate more conservatively - 24 x 2 x 4 = that already is 192 cu inches, close to the limit.
[3] All four fish are only beginning to grow.
[4] It is a bad idea to feed items of non-aquatic origin to aquatic animals such as RTC, especially meats from warm-blooded animals, and especially as fatty as commercially raised chickens for human consumption. The fat solidifies at the RTC body temp (same as water temp) and is deposited around vital organs leading to a premature degradation and death.
