Syphoned out almost all the sand: there were some patches of red flap and especially under the skimmer a lot of mud had accumulated at the bottom of the sand. Replaced it by a thicker layer (avg. 8 cm) of sand (half normal aquarium grit, half special reefsand) to create an anaeroob environment, to get the denitrification bateria society started. Also added Tetra nitraMinus pearls to inoculate the fresh sand.
Nitrate wasn’t too high after all today (between 10-25) but decided to carry on for it also gave me the opportunity to refresh the water for 50% and shrub away algae from the rocks i had to lift out anyhow.
wimszeewater 