Orca Bio Cube Nitrate reducer I have 10 x 1lt Orca bio cubes to reduce nitrates. I have personally used it on all my tanks and it is awesome coupled with a good skimmer. Recommended dosage is 3ml/100lt There is no risk of overdose as it only works to reduce nitrates if they are available. Jus soak in RO water 24hours before placing in the sump. R550-00 each / 1lt Shipping for buyers account - Counter to counter or Postnet Items can be picked up in durban.