I would place it so that it helps, not hinders the current from the filters. There are 2 places that this could work.
1 is near the top of the tank, either between the 2 filter outlets or in a corner, but essentially aimed in the same direction as the filters, the other location is near the bottom, on one end or the other. This will help keep things moving on the floor of the tank.
With ammonia that high I would be doing a lot of water changes. Keep testing, keep changing the water to reduce the ammonia, keep it under .25 ppm, and use an ammonia locking dechlorinator. The nitrifyifng bacteria can utilize ammonia that is locked up, allowing the bacteria population to grow to match the ammonia production. Ammonia removing minerals (Zeolite, ammo chips) removes the ammonia from the tank, starving the bacteria.
Looks like running the filter media without any food did not allow too many bacteria to survive.
Look out for a spike in nitrite. When this happens do enough water changes to keep the nitrite under 1 ppm, and add 1 teaspoon of salt (sodium chloride) to the tank per 20 gallons. This will minimize Brown Blood Disease.
