June 7 2012
After restarting the refugium late in April I had some problems with getting good growth. There were 2 small blooms in May, but most of the time the refugium was in "crash mode". During the problematic periods I lost patience and scraped out a lot of benthic algae. Now in early June the growth is good again. The harpacticoid population is large. I suspect that they contribute to the growth of phytoplankton in a positive way by eating the benthic algae. So finally I can start thinking about measuring their food contribution again. I don't have much new to report in terms of display tank animals. As usual the clams are showing good growth while anemones, corals and sea squirts are lagging a bit behind. I have had blooms of many smaller animals though, like some very small worms living in the sand bed, and small bryozoa.
Dragonet (Callionymus lyra). Freediving picture.
I did an honest attempt at fixing my Titan 1500 chiller. It was leaking in the bulkheads where the cooling loop tubes, and temperatur probe, enter the heat exchanger. The first plan was to open the heat exchanger so that I could clean or replace the main gaskets on the underside. So I drilled out the rivets that held the heat exchanger together. But it turned out to still be impossible to get it apart. Apparently a rubber gasket was glued in place under there. At this point it dawned on me that it wouldn't necessarily help if I could get it apart. The reason was that since the cooling loop is soldered as an unbroken circuit it would not be possible to change any gaskets. So cleaning was the only hope. The main gaskets of the bulkheads, between the heat exchanger and the bulkhead screws, seemed to be glued in place. So the only hope for repairing that would be to use silicone in the hole. But I decided to first test if the problem was caused by the small gaskets between the tubes and the bulkhead screws since these were not glued, seemed rather dry but still in good condition, and would be very exposed to thermal movement of the tubes. It was possible to rub them thoroughly with vaseline. After retightening the bulkheads I did a few short water tests, and I could not see any leaks. So I hope it is working now.
It was leaking in the bulkheads which you can see as large white screw nuts here.
Drilling out the rivets was no use.
I have some exciting plans ahead now. I am thinking about setting up a zooplankton refugium in addition to the phyto refugium. I have not succeeded in getting any zooplankton to reproduce in significant numbers in the phyto refugium. I have tried to set up a net that blocks the large specimens from beeing washed out. But they consistently die after relatively short time. This happens even at temperatures that they should be able to survive at. My best hypothesis is that they are killed by bacteria and sticky detritus in the dense soup that is the phyto refugium. The zooplankton refugium will allow me to test it. I plan to set ut up with 2 input flows: One will be the regular output flow from the phyto refugium. The other will be a much higher flow from the display tank. I haven't decided the DT flow yet, but it will probably be closer to 1x/hour than 1x/day. This will solve all temperature issues. If the flow is high enough it will keep the water clean, and at the same time transport enough phytoplankton to the DT. However, high throughput causes problems too: The biggest is washout. I hope to remedy this with a net on the overflow hole. But juvenile zooplankton will get washed out at a rate proportional to the flow. This can to a degree be offset by using a net with small mesh size. Tuning in mesh size and flow rate will be complicated and time consuming, but an important part of the project later. In the beginning it will just be to figure out if it can work at all. Another major issue is the fact that this refugium will work as a large sedimentation filter for the phytoplankton, stealing food from the system. Internal circulation and higher throughput will help to reduce this. All in all, only practical testing can give answers to wether this will work or not. Two major goals must be reached to call it a complete success: It must produce large amnounts of zooplankton, and it must not steal too much phytoplankton. Still, if it just reaches the first it will be a great success.