ARMS Assembly

During this step, you will be assembling the ARMS units from the individual parts. The unit is a stack of alternating open layers and closed layers. The closed layers contain a cross-shaped structure dividing the ARMS in four compartments, providing "cave-like" spaces for organisms. The very first space, at the bottom of the ARMS should always be a closed layer and the top layer will be open.

Another important feature is that the first plate should lay flat on the base plate. No space should be created between the first plate and the base plate in order to avoid creating an extra space for colonization.


  • 1 x PVC base plate (45cm x 35cm x 1.27cm)
  • 9 x PVC layer plates (22.5cm x 22.5cm x 0.63cm)
  • 4 x PVC long cross spacers (30cm x 2cm x 1.27cm)
  • 8 x PVC short cross spacers (14cm x 2cm x 1.27cm)
  • 4 x 7½ or 8-inch stainless steel bolts – 2” thread length
  • 16 x ½-inch long Nylon spacers
  • 12 x ¼-inch stainless steel washers
  • 4 x ¼-inch stainless steel nuts
  • 4 x ¼-inch stainless steel nylon insert locknuts
  • 2 7/18-inch wrenches
  • Silicon grease or Aqualube/AquashieldTM


  1. Place a washer on each of the stainless steel bolts and run the four bolts with washers through the four corners of a single layer plate. Invert the plate so the bolt heads and washers are underneath and the bolts are sticking up through.
  2. Slide a nylon spacer onto each bolt and add a second layer plate. This creates an open layer (this will become the top layer when you invert the entire stack onto the base plate later)*.
  3. Slide a long cross spacer onto two bolts in opposite corners. Place two short cross spacers on each of the two remaining bolts (one each) in a way that they make contact with the long spacer at right angles. Add a third layer plate to create a closed layer.
  4. Repeat steps 2 and 3 to alternate between open and closed layers until there are four of each.
  5. Once the fourth closed layer is complete, put silicon grease to the threads of the bolts and add a washer and a nut to each bolt; tighten securely.
  6. Place the base plate on the bolts with the counter sunk side down. Coat the tips of the bolts in silicon grease again if needed. Add a washer and the locknut and tighten securely using the two wrenches - one on to hold the bolt and the other to tighten the nut.
  7. Invert the ARMS structure so the base plate is on the bottom. It is now fully assembled.

*Note: the layer directly above the base plate should always be a closed layer. The plate in contact with the base plate is the plate #1.


ARMS spare parts: 1 base plate - 9 PVC plates - 4 long cross spacers - 8 short cross spacers - 4 stainless steel bolts (7.5" long) - 12 nylon spacers - 8 nuts - 12 washers - 4 locknuts

Schematics of ARMS assembly

ARMS assembled and ready to be deployed


David Weinstein (not verified) commented on 12/11/2017 - 05:05 - Permalink

I am not sure if you do this, but it might be a good idea to weigh the experiments before and after deployment as another metric of changes to the system. We have done this often to understand how carbonate is added to a particular reef area. If you want to discuss, you can email me at

Laetitia (not verified) commented on 04/24/2018 - 18:13 - Permalink

Hi David,
We have never weigh the unit after deployment. Do you usually use dry weight? We do scrape of all the communities and get data of biomass.