I have a used Precision Marine Bullet 1 with a new Mag 18 pump on a 75-gallon octopus tank. The skimmer is running outside the 10-gallon sump (can't fit anything larger under the stand). I use only RO/DI water and my parameters are pH 8.2, Nitrite 0, Ammonia 0, and Nitrate 40. Other than at...