Alexander Foreman's page

The 9000 Litre aquarium project


Engineering the mega tank

Check out the forum discussion at monster fish keepers.


 Basic idea:

  • Make a monsterous aquarium to satisfy my fish obsession
  • Place the aquarium outdoors, against the living room window to create a view into an underwater world
  • Make the aquarium so big that I can get into it and interact with my fish

 List of wants:

  • Budget: $5,000 to $10,000 AU
  • Reasonable portability and flexability in case I move
  • Natural sunlight to bring out colour in fish
  • Energy and water efficiency
  • Maximum automation to minimise maintenance
  • A "vertical reef" full of plants and hiding place
  • Two wells so the tank can be drained and the fish placed in one well so I can work on the tank without removing the fish 

Current plan:

  • Develop tank design
  • Learn to MIG weld
  • Weld small scale version of tank
  • Galvanize small tank
  • Paint interior with epoxy resin
  • Silicone in glass window
  • Make tower trickle filter
  • Test small tank with live fish
  • Finalise large tank design
  • Lay foundation
  • Build tank (same process as small tank)
  • Pressure test in safe location
  • Install

(Dimensions are approx 9' long, 6' wide, 7' high)

Conservation plan:

  • Glass windows and lids double-glazed to minimise heat loss
  • All other internal surfaces covered with 10mm high density styrafoam covered with pond sealer to complete insulation and form visual background
  • Pool solar heater with secondary electric heater
  • High efficency trickle filter to minimise pumping requirements
  • Skylights to minimise need for electric lighting
  • Overflow plumbed into garden sprinkler
  • Attached garden tap and pump for outdoor water use such as car washing and watering



To all the people that have helped me develop this project I would like to offer a huge thank you!

  • Thanks to the Monster Fish Keeper guys, especially:
    • cvermeulen - for unlimited patience and technical assistance as I blunder along!
  • Thanks to my wife for understanding my obsession
  • My work buddies who have freely offered their knowledge:
    • "Coffee cup" Tommo - for technical info on pressure bearing vessals
    • Justin M - for framing and metalwork advise


Filter plan:

Modular filter system:
  • All mounted on rear cross base
  • Up to 4 modules
  • Easy to modify filtration system
  • Filtration can be increased or reduced depending on bio-load
Module design:
  • 10,000 litre per hour submersable pump
  • Overhead solar algae turf scrubber
    • Area:
      • Area rule of thumb of 3.6 square cm per litre = 3.6 X 9,000 = 34,400 square cm
      • Module = 1/4 of filtration = 8,100 square cm
    • Size:
      • Therefore I could use 3 60cm x 45cm screens
      • Set up in parallel for ease or removal
      • Total of 180cm of watefall pipe
      • Perspex covers prevent cooling
    • Water flow:
      • Flow rule of thumb 53 L/h flow per cm or waterfall pipe = 9,600 L/h
  • Modify a set of office storage trays:
    • Drill holes in bottom to create trickle
    • Set up in a frame so they can be pulled out like draws
  • Make frame from tubular steel with angle to support draws
  • Use a solar algae turf scrubber for nitrate reduction and cooling in hot weather



  • Soft steel 10mm frame consisting of wide flange beams and angle iron
  • Plate steel or glass / perspex windows make up all panels
  • Steel is welded together
  • Steel is sealed with liquid rubber, not galvanized or otherwise treated
  • Windows are seated in a gasket of silicone / polyurethane adhesive
  • The tank has no stand, it sits on a concrete slab and is buffered by a layer of foam


  • Tank will be outside and exposed to elements
    • Must be UV resistant
    • Must be insulated
  • Cost must be kept down
    • Use of smaller panes of glass to reduce thickness requirement and therefore expence 
  • Will be welded at home by me
  • I am currently learning to weld

Lateral framing plan

  • Angle iron top and bottom frames
  • Wide flange beams used for cross braces
  • All lateral frames are mitered

Vertical framing & top bracing plan:

  • Angle iron butt welded at corners between lateral frames
  • Additional angle may be added to assist framing the windows
  • A supporting top brace angle will support the overhead filter system
  • Rest of top bracing is flat iron

Plate steel plan:

  • Plate will be welded over all areas not used as windows
  • I intend to increase plate thickness as depth increases
  • A central plate acts to brace the tank and create 2 "wells" in the bottom of the tank

Sealed with liquid rubber and sandstone coloured top coat

Viewing windows plan:

  • Windows are divided to reduce expence and improve ease of construction
  • Undecided as to use glass or acrylic
  • Windows will be seated in a silicone or polyurethane adhesive bead 

Glass plan:

  • According to my calculator I can safely use 12mm annealed glass for all windows. I am inclined to go to 16mm for safety. Constructive feedback would be appreciated.
  • The frame must support the glass so it does not exceed:
    • Maximum glass deflection = span/1000 = 2.3mm for front and 1.6mm for side windows

Acrylic plan:

  • Max acrylic deflection = not determined
  • Acrylic longengevity outdoors = not determined


  • 9720 litre (2570 gal) capacity
  • Estimated total weight = 11 to 12 tons
  • Max acrylic deflection = not determined

Lateral load of water pressure (including frame)