June 11, 2015
I did a large restart in late april and seeded with several species of calanoids. In addition I kept some of the water in the bottom of the phytoakvarium so I didn't have to reseed the benthic fauna. However, after 7 weeks the symptoms have been exactly the same as last time: Just a slow die off of the calanoids. At the same time, ciliates, dinoflagellates, medusae, and benthic copepods are reproducing at a good, but not spectacular, rate.
Copepods, mainly Temora longicornis are gathering together in the light cone from a flashligt.
This, and the two next pictures, are the same scene as above, but taken with a 60 millimeter macro lens. The copepods are mainly Temora longicornis with their characteristic round backs.
In this picture there seem to be a couple of barnacles too.
I found a document online called "The identification of the copepodite developmental stages of twenty-six North Atlantic copepods", by David V.P. Conway, from the UK. This doesn't cover all possible species, but I hope that it covers the most likely ones. Based on this guide I am pretty sure I have identified 3 of the most common species in my tank: The larges ones are, as expected, Calanus finmarchicus. The ones where the females carry round egg clusters are Pseudocalanus elongatus. Another rather characteristic species that I have is Temora longicornis. It was really great being able to identify these. It is so useful to be able to look for sources on them on line.
I got some problems with the phytoaquarium this time. I decided not to dose silicone to get other types of algae than before. That worked. After a couple of weeks the amount of diatoms went down. But I never got a good bloom of other phytoplankton. One of the issues is that some purple film forming algae, probably cyanobacteria, have established themselves really well on the sides and bottom of the tank. They grow at very large rates. I can scoop out large amounts every week. But they come back fast. So a full restart from dry seems to be the right option at this time.
A week's growth of benthic algae.
When working with the algae growth I decided I had to install my trusty old American Marine Pinpoint pH monitor. The problem with a pH probe in an algae aquarium is that it gets fouled with algae and useless within a day or so. I never solved this problem before. This time I tried, and hopefully the very simple solution will work. I haven't used it long enough to conclude yet. I just took a piece of 32mm PVC pipe and drilled a hole in it for the probe's suction cup holder. Then I found a black bottle cap that could be placed loosely on the top. Hopefully this will keep the probe in the dark and shield it from algae fouling. The pH has been on a pretty steady 8.7 so far.
Making a pH probe cover from PVC pipe and a bottle cap.
Way less light on the probe now.
I decided to test something I have been thinking about for years: Is it possible to keep some sort of snails or limpets in the phytotank and have them contribute to keeping the algae growth on the walls and bottom down while at the same time recycling nutrients and producing CO2? So I went out and got 10 limpets and 16 shore snails (periwinkles). It did not go well. I knew that the environment in my aquarium could be hostile to some molluscs. But this surprised me. 6 of the limpets died within 2 days, and the rest just stood completely still without any movement. The periwinkles did a little better, but after a week 1/3 of them had died too. So I concluded that the environment in the phytoplankton aqaurium was not right for them. What is the problem, I wonder. Could it be some shock related to pH? 8.7 is high. I didn't do any acclimatization. I have noticed that the benthic copepods don't do that well in the phytoplankton tank in this project. The only difference I know of is that in the last project I dosed CO2 all them time, keeping the pH at about 8.2. So pH is a possibility.
Limpets (Patella vulgata) and periwinkles (Littorina spp.)
A rather dead crowd of limpets, after 2 days.
Counting periwinkles after 2 days: 3 out of 16 Dead.
I have been working on plans for a filter for the system. The goal of the filter is to reduce the amount of toxic and hard to break down metabolites in the water. I have no idea if it will have any positive effect, but it is certainly worth trying. I would like a filter that uses ozone and activated carbon in combination. But it must be plankton friendly! It must work so that it processes only a small amount of the water in the system per day, and return only "safe" water to the system. I think I have reached a satisfying design now. I am planning to modify my trusty old Deltec APF600 skimmer into this. Even without ruining the skimmer. It can be brought back to its original order later on. In addition to that I will do some more experiments with snails to see if I can shed some light on what is actually causing problems for them.