December 2 2012

Nutrient switch

The new Guillard F/2 nutrient formula seems to be much better than my old one. The old one worked, but it tended to give crashes, especially in the beginning. There were also periods where it was hard to reach high concentrations, which resulted in benthic algal growth. The new solution gave excellent growth from the start. A bloom more dense than anything I have seen before came, and just kept going in a very stable way. The feeding rates are up to 8 grams per day of algae biomass. The pH can be kept stable at 8.2 for long periods with 20 bubbles a minute of CO2. The feeding response of the animals is great. So this is definitely the way to go. I have been working with tuning in the dosing regime the whole of the past month. Early on the pH in the refugium rose to 9. So I started dosing CO2. Because of the strong discoloring of the refugium water it was difficult to measure nutrient concentration with the test kits. So I started measuring in the display tank instead.

Phytoplankton refugium

Great growth is coloring the water dark red-brown.

pH monitor

Refugium pH without CO2 dosing.

Nutrient overdose

Nutrient overdose! At one point, while tuning in the new nutriet dosing, I dosed too much nutrients. The phosphate is way off the chart here.

Predators, grazers, parasites

The last month I have focused a little bit on removing some of the "pests" of the aquarium. First of all I want to get rid of as many sea spiders as possible. These are truly strange creatures. They belong to the same phylum as spiders and crustaceans, but are not closely related to any of them. They move extremely slowly and slowly find and eat anemones. The large ones, like shown on the picture below, eat up small anemones completely. I have also decided to remove scaled snails, chitons and limpets, that keep surfaces clean of growth. I want benthic animals to grow on those surfaces.

Sea spiders pycnogonids

I have removed more than 10 sea spiders the last month. Notice how they are munching on that little anemone!

Horse mussels

I finally got around to measuring my two oldest horse mussels (Modiolus modiolus). The largest had grown from 70 to 79 millimeters, and the smallest from 66 to 76 millimeters. This should give a 44% and 53% weight increase, respectively.

Horse mussel, Modiolus modiolus

Horse mussel (Modiolus modiolus).

Zooplankton refugium

I am really eager to set up the new zooplankton refugium now. The new nutrients have made the outlook for success much better. I am currently deep in the theory of how to allow the zooplankton to reproduce in the new refugium. Dilution rates, mesh size on the overflow net, growth rates, mortality rates are things I am looking into. So far the conclusion is that it may be very hard to get enough reproduction to allow a growing population of zooplankton. But it may be possible to have a population of adults that are continously producing large numbers of offspring for months before they die.

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