The filter is a 50mm diameter tube with a 50mm plastic union. Inside the union there is a plast with a 25 mm diameter hole, the white filter paper sits over the hole.
The filter paper is centred and the union screwed together, this secures the filter paper.
The tube has a water volume of 500ml, so you just fill the tip to the top, some water will escape quickly through the holes used to suspended the filter, this has been accounted for in the design.
The filter is now just suspended for up to 60 minutes the filter the water sample
The following is a drawing of the filter, if you wish to make your own filter, you may construct according to this design.
Unfortunately it is made from plastic, but it should last for many years. It is made from 50mm pvc plastic pipe, with a PVC union fitting. There is a 60mm diameter x 5mm thick disc in the union, with a 25mm hole. The filter paper sits on top of the disc.
The pipe is solvent glued into the union.
The filter is really easy to make if you have access to professional pipe fittings, but you may also be able to make one with fittings from a good plumbing store.
50mm diameter, 0.45um pore size
Any good quality, stainless steel tweezers will be okay
Use a 90mm diameter Petri plate, it also allows you to cover the sample and keep. Please note that if you wish to keep the sample, it will need to be dried. Wet plankton samples rapidly deteriorate and have a really bad smell. The petri plate is made from glass, and is reusable. The plastic ones can also be reused many times and might be safer on a boat
Below is a 5mm squared 50mm waterproof paper disc. This is used underneath the filter paper when viewed under the microscope. The black lines will show through the filter paper and allow you to track your position on the paper, so you count particles in each area only once.
The GOES team will free issue you with the paper. It can be washed and reused many times.
Microscope ruler for calibration
We are going to be measuring size groups of plankton, so you need to be able to calibrate the microscope.
We will also supply 50mm water proof paper discs, with 5mm (5000um) squares. You can also use the squares to get an idea of scale. Some camera software allows you to set up a scale on the image which then makes it easy to measure objects.
The resticule is not 100% required, but it can be useful.