Constructing the Squeegee Siphon Assembly

The squeegee is designed to gently scrape the bottom of the tank to retrieve the eggs produced since the last harvest. A siphon hose alone will not capture all eggs entrapped in the biofilm that builds up in living systems. The tool needs to conform gently to the bottom of the tank without damaging the Fiberglas gelcoat. Plumbing diameters need to be sized to maintain siphon velocity and flow without overwhelming the stacked sieves. Many alternate strategies could work. Our solution was to construct a simple siphon from PVC and install a section of Shop-Vac squeegee (an accessory for the wet vacuum head) as a scraper (Figures 8, 9, 10).

For a 300 L tank, construct a ¾” (1.9 cm) I.D. PVC siphon assembly:

¾” diameter PVC pipe, at least 60” long

¾” PVC tee fitting

¾” PVC couplings

¾” PVC 45° elbow

¾” PVC female fitting

¾” PVC male to hose barb adapter

7’ (2 m) section siphon hose

¾” Hose clamp for siphon hose

6”- 9” (15-23 cm) section of Shop-Vac squeegee

PVC discs cut from 4” PVC test caps

Large report-style paper clamp

Figure 8. Squeegee Scraper

1.Glue the PVC tee and couplings together with sections of pipe to fill the interior voids as completely as possible. 6”- 9” (15-23 cm) siphon head width is the optimum width for this design.

2. Use a Dremel tool or hack saw to slice a slot opposite the tee inlet, cutting through both the fittings and the PVC pipe glued inside. The slot’s interior faces are cut parallel, not splayed apart. The slot’s width matches the width of the Shop-Vac squeegee, measured under the outer flange. Trim a section of squeegee to fit and cement in place with silicone aquarium sealant.

• Cut discs of PVC and glue to the ends, positioned to allow the squeegee to just deform as it moves across the bottom of the tank.
• Attach a length of PVC pipe sufficient to reach beyond the upper lip of the tank to the tee.
• Glue a 45° elbow on to take the following sections by friction.
• Glue on a short section of ¾” PVC pipe to the slip x female PVC fitting,
• Screw into the female PVC fitting the male PVC to hose barb adapter.
• Clamp the siphon hose to the barb adapter,
• Slip the wire wings of a large report-style pinch clamp over the hose to allow the clamp to attach to the stacked sieves to hold the hose in place.
• Let all parts stand for 48h to allow all volatile elements of the glue to dissipate.
  

Use of the Squeegee Siphon

• Sanitize your hands with 70% isopropyl alcohol or wear latex gloves.
• The siphon head assembly remains in the tank, sanitized during tank treatment.
• Connect the siphon hose assembly to the siphon head assembly (friction fit).
• Initiate siphoning by providing suction.
• Clamp the siphon hose to the stacked sieves.
• The squeegee assembly is slowly swept across the tank bottom, starting from one corner and proceeding deliberately in a regular pattern.
• Do not stir up the eggs and detritus on the bottom as you proceed.
• When done, remove the siphon hose assembly; leave the siphon head in the tank.
• Rinse the siphon hose with a wash bottle, drain effluent into the sieves.
• Remove the siphon hose clamp from the stacked sieves and process the collection

Figure 9. Squeegee cross-section schematic.

Figure 10. Squeegee longitudinal section schematic.