Installing the mechanical filter, cleaning it once a week, transferring the fish to the system when needed or maintaining the tank and biofilter were tasks I also carried out. This section shows the weekly track of the system.

Week 1

At the beginning of the week 1, I went to the company where they had the biofilter with the bacteria to disassembled and take it to the university (PiE-UPV/EHU). We did the installation in the marine station with two representatives of the company with an empty tank at the beginning. The biofilter was fed in the company with artificial feed (ammonium and glucose), the transfer to the PiE-UPV/EHU was in order to start trials with fish and natural feeding (fish droppings).

I learned the procedure of the introduction of the fish in the system. For the RAS trials I employed the species of mullet Mugil cephalus. The fish were in another tank and we took them with a net to a little tank with anesthesia (2-Phenoxiethanol). The concentration of anesthesia was of 3ml in 10L of water. The number of fish anaesthetized were 30 and we proceed to measure and weigh them. After, we transferred them into the system with a total biomass of 1,2kg.

Week 2

At the week 2 of the PP, the ammonium levels where too high and there was no presence of nitrite and nitrate in the system. I ask to my mentor to take out the fish from the system as those levels of ammonium were toxic.

Week 3

As the water had high turbidity levels, I thought that a mechanical filter was needed (as there is in every RAS). Maybe bacteria were saturated of organic matter as the carriers were very full, so hopefully that was the cause of the lack of nitrification. At the beginning of week 3 the mechanical filter was installed.

Week 4

As the ammonium levels were going down and there was presence of nitrite, we decided to reintroduce fish in the tank, but now a lower biomass, in order to see if the bacteria of the biofilter are nitrifying correctly.

Week 5

The first cleaning of the mechanical filter was performed. At the end of the week 5, as the ammonium levels and the nitrite levels of the system were high, we decided to take out the fish of the tank until the levels decrease. I thought it could be also because the flow rate was too high so we decided to decrease the flow in order to have more remaining time of water in the biofilter.

Week 6 and 7

I did trials with fish droppings as the levels of toxicity of ammonium where too high to have fish in the system.