The last month I performed two seedings of the refugium. The first was with my old setting of 40% flow per day, 24 hours lighting and dosing of nitrate, phosphate, silicate and Seachem Flourish nutrient solution. The diatoms bloomed immediately, so I started dosing artemia cysts. I doubled the dose this time to 0.64 grams per day. During the second week the algae bloom crashed. There were now lots of adult artemia in the refugium. I don't know what caused this crash. I am speculating that it could be the artemia population being so large that it ate all the algae. But I don't really think so. It could be the good old mysterious nutrient crash that I have seen before. When diatoms start declining they just disappear completely. They are not just reduced to a low concentration. The water goes completely crystal clear.

I decided to empty the refugium and start over again in mid month. I must admit I am not particularly good at changing one thing at a time. A little bit too eager maybe, but there are so many things that must be tested that it would take endlessly long to be completely systematical about it. This time I increased flow to 55% per day. I allowed a dark period of 4 hours during the night. I dropped silicate dosing to change the type of algae. I wanted to try something else than diatoms for a change. But there seemed to be a lot of silicate left in the system because the first bloom was the typical diatom bloom. Artemia dosing started after one week at 0.48 grams per day. The temperature in the refugium has gone down from 26C to 23C. The higher flow or the lower temperature has affected the artemia, now it takes much longer before adults are seen in the refugium. It may be that they grow more slowly or that they are washed out fast enough to prevent them from reaching adult age. This may be a good thing since I don't want the artemia biomass to be so high that it crashes the phytoplankton culture. At the time of writing the refugium has been running for 4 weeks and is still in a fairly stable bloom state. There are macro algae growing some places in the refugium. Among others, something that looks like Ulva enteromorpha. These can grow fast under the right conditions. But they don't. Another indication that there is something mysterious and growth limiting in the refugium. Grazing and washout is not an issue for these macros.

Flow

I now realize that the display tank may have had much too little flow. I thought the Eheim Compact+ 2000 that runs the chiller loop had enough flow to generate a good circulation. But when I mounted a separate MaxiJet MJ1000 I realized how little flow it actually provided. The chiller is extremely restrictive on flow because of the silly inlet/outlet valves. So I put in an MJ1000 next to the outlet to help it spin the water. Now I can see that there is good flow in the display. I really hope that the anemones and corals will do better now. The amount of dirt particles in the water has gone up though. But I hope it clears up after awhile.

Growth

I measured the growth of some clams last month. More specifically the original group of blue mussels, the oyster and the one scallop that I actually measured when I caught it. They had all grown a bit, but the oyster has grown very much. Apart from the burrowing clams that died in the start most clams have grown quite a bit. The blue mussels had measureable growth of 2 to 7 millimeters. The small ones had grown the most. In addition to the clams that I introduced on purposes there are dozens of small blue mussels and wrinkled rock borers (Hiatella arctica) that have come as minute speciemens on rocks, or even larvae. These have grown significantly and are rapidly becoming a visible part of the tank fauna. So things are certainly looking good in terms of clams. When it comes to the sea squirts, most are still alive, but I have also lost quite a few of them. The brittle stars are feeding and seemingly doing OK.

Sucky pH controller

I tried to install my American Marine pH controller a few weeks ago. So far I've been very impressed with American Marine products. I've used their pH monitor and RedOx monitor. But this time I was very disappointed. The product gave a relatively bad impression in general, but the worst was that it made a loud humming and rattling sound. I didn't dear using it at all in the end. I may test it a little more and see if it works. This product is not recommended! In general CO2 is really expensive, difficult and dangerous. The achilles heel is the pH probe, which is completely unreliable in the environment of a phytoplankton refugium. So I am still opening and closing the needle valve manually. But I think that it may be better to not use CO2 at all.

Freediving

Finally I have started freediving! In the weekend of 6th and 7th of August I took classes. On the second day of the course we went diving and were in the water for more than 5 hours! Not cold at all even though it was raining. Currently I am training breath holding, pressure equalization, and swimming with fins. It is quite a bit of training to be a good freediver. And you need to be relatively good to get down to about 5 meters and have time to look for things down there. I've been out diving 4 times so far, and found some nice dead man's finger specimens that are larger than the ones I have, but small enough to fit perfectly into my display tank. The water is so warm now that it is not necessary to have gloves on. So I am free to work with my hands under water. In addition the corals I have found some nice plumose anemones and one small dahlia. Now that I am feeding artemia it will be exciting to see if they thrive.