August 1 2012

The Newcomers

As shown in last month's update I added some predators to the aquarium to reduce the number of blue mussels. After the update I added two more common sea stars (Asteria rubens). So now I have 4 common sea stars and 5 dog whelks (Nucella lapillus). The starfish started by eating all the barnacles on the right side wall. It was incredible how easily they took them. They were gone within a few days. But after that they seem to have eaten mostly the things I had hoped for, namely the mussels. It is theoretically possible to see which mussels are eaten by sea stars and which ones are eaten by whelks since those eaten by whelks should have a small hole in the shell.

Mytilus edulis shell

This mussel has probably been taken by a dog whelk since the shell has a tiny hole.

Asteria rubens

In the middle of this picture you can see a sea star in the process of opening a mussel.

Zooplankton refugium

The zooplankton project is rolling forward at a steady pace. I have now built a new stand and bought virtually everything I need. Now I will first build the double glass, then insulate the other sides with styrofoam, then drill the tank and install plumbing. Finally I must empty the phytorefugium because the new stand will be under that. The phytorefugium will be the highest of the tanks. The water will flow from it down to the display tank via the zooplankton refugium.

Zooplankton refugium

Zooplankton refugium being set up. The stand it is on in this picture is the highest and will be under the phytoplankton refugium when the installation is complete.

Zooplankton refugium

Styrofoam stress tests

The styrofoam stress tests are finished. The deflection was a bit higher than I had hoped for. But it should be possible to make an aquarium from it. I got the feeling that the styrofoam clearly was the weakest link in this laminate. The number of layers of fiberglass did not have all that much effect on stiffness. With 2 layers on each side the deflection was 13.5 mm with 80 kilos. With 4 layers it was 11.5 mm with the same weight. Also, with only 20 kilos the deflection was 4.5 mm in both cases. I know enough to make aquariums for myself this way, but to make them cost efficient and to make a calculator I need much more physics knownledge. Maybe I'll have the energy to get that knowledge in time.

Stress test
Stress test

Stress test of 2 layers of fiberglass cloth with 60 kilos.

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