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Emperor 400 - Power Filter Tricks
by William McReynolds

This is a more challenging power filter to properly optimize. But, with a 400 gallon per hour flow rate, two very large bio-wheels, and a pair of customizable media trays, the potential modified performance boost to this filter, is definitely well worth the work! Completing these steps will convert an already quite respectable performance, into what may possibly be the best performing biological filtration power filter system you can buy. The trick to accomplishing this feat, is aeration of the customizable media trays. Creating a 'reverse action', mini-sized, wet/dry trickle filter!


Instead of the standard wet/dry filter method of water trickling and splashing DOWN over (dry) rock media - air is pumped and bubbled UP inside the media trays through the (wet) rock matrix media of the fully Optimized filter!


  • (1) Pair of Scissors
  • (1) Single Edged Craft Razor
  • Dremel Tool, (or Hacksaw Blade)
  • Electric Drill and Bit


  • (1) Mag Drive Models 9.5 - 18, submersible pump, foam pre-filter
  • (1) Rubber Band
  • Length of Regular Sized Air-line Tubing
  • (1) Air-Line Tubing 'Tee' Fitting
  • (1) Small Container of either Kent, De-Nitrator Matrix or Eheim, EHFI Substrate
  • (1) Air-Line Tubing One-Way Check/Safety Valve
  • (1) Small Capacity (quiet!) aquarium air pump

Optimization Steps

  1. Remove the 2 blue colored, filter foam/plastic filter screens from the power filter. Using the single edged Craft Razor, carefully cut a slit down one side of the blue foam for each filter screen. Dump the carbon granules inside each screen into the trash if they are used, or save unused carbon in a zip-lock bag for later use, if desired. Rinse empty filter screens in de-chlorinated water, then re-fill each filter screen with pre-rinsed matrix rock. Re-install both foam filter screens into the filter.

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  1. Pull and discard the plastic insert piece out of the Mag Drive Submersible Pump Pre-Filter. Cut off approximately 1/3 of the foam from the top of the filter, where the insert piece went in. Next, take the scissors and single edged craft razor, then carefully cut and shape the foam piece to fit the box intake of the power filter. Enlarging the intake hole in the pre-filter with a bit of reduction in the external size of the filter will make for a neater/cleaner appearance. The finished foam pre-filter should appear similar to pictures shown. Secure mounting of the foam pre-filter onto the box intake is accomplished with a rubber band.
  2. Pull both empty, gray colored, plastic media trays out of the filter. Separate both top and bottom marked halves. Use a Dremel tool to cut slots in the bottom marked tray's plastic reinforcing ribs that are large enough for the airline tubing to fit down into the tray. Cut smaller slots on both sides of the cut out airline tubing channel to facilitate trickling air flow, up through the media tray. Note: A Hacksaw blade can be used to cut slots in plastic media tray reinforcing ribs, if a Dremel Tool is not available to do this.

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  1. Next, take the top marked media tray and drill a single hole in the top large enough to accommodate the airline tubing. Use a smaller bit and drill a smaller hole on each side of the drilled out, airline tubing hole, on top of the filter media tray half.
  2. Place the air stone with airline tubing down into the bottom marked media tray.

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  1. Fill the bottom media tray with pre-rinsed matrix rock until slightly higher than the plastic reinforcing ribs.
  2. Route the end of the airline tubing mounted in the bottom media tray, up through the large, middle hole drilled into the top media tray. Pulling the excess airline tubing through the top media tray, drilled out airline tubing hole, carefully close and snap the two plastic, media tray covers together. Gently shaking the matrix rock inside the media tray will help to securely close the media tray when doing this.

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  1. Place the media trays back into the filter. Cut off excess airline tubing until the 'tee' connector fitting will sit down in front of the filter's flow rate adjustment handle, under the plastic filter cover. Connect a single length of airline tubing to the 'tee' fitting that will be routed up and out of the filter to an air pump.
  2. Simply route the single end of the airline tubing up through a center vent slot of the plastic filter cover, and set the cover down on top of the power filter. Install air-line tubing one-way check/safety valve on air-line tubing length going to the air pump. Mount the filter onto the aquarium, connect an air pump up to the single length of airline tubing, prime the filter with water - and you're ready to go!

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Operation Of The Optimized Emperor 400

  1. The Foam pre-filter must be carefully cleaned in de-chlorinated water with each water change to insure high rates of water flow through the filter. Periodically replace the securing rubber band when it becomes worn.
  2. Clean the Blue Foam/Plastic Filter screens foam periodically to insure high rates of water flow through the filter. Frequency of required cleaning of this power filter will vary considerably with the bio-load of your aquarium, water chemistry and other factors. Over time, (months?) the blue foam on the filter screens will become worn and due for replacement. Replace the filter screens with new ones when this occurs - But, NEVER discard the matrix rock inside the filter screens! Simply dump the rocks out of old screens and put the now filtration bacteria-colonized matrix rock into the new blue foam/ plastic screens (after the new screens are slit with razor and carbon granules are dumped out).
  3. Periodically clean and rinse in de-chlorinated water the matrix rocks inside the media trays. NEVER discard or replace this media! Replace or clean the air stones inside the media trays when air flow becomes restricted and there is no longer vigorous air bubbling noted through the rock matrix in each media tray.

Responsibility Disclaimer: By performing any of
these alterations or modifications to your power filter, you agree that the Author
and Cichlid-Forum are NOT Liable for any problems or damage that may occur
as a result. Manufacturers should be contacted first prior to any modification
or alteration being performed to this equipment if doubt exists concerning the
ultimate proper and safe operation of aquarium filtration equipment modified from
the manufacturer's original specifications.
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