The purpose of this calculator is to help familiarize yourself with the interactions between the various influences in aquaculture design. This is a basic calculator specifically for aerated systems and goes hand in hand with our recent aquaculture design introduction webinar. It does have limits so please feel free to use it but at your own risk and check all results are correct before applying them to your particular system. This is a Beta version which we will update as bugs come to light. A brief outline of the workings of the design calculator It is very easy to use.  Simply input the amount of fish you want to grow in a year, select imperial or metric, then adjust the sliders to suit your situation.  We will release a more technical calculator at a later date which will make the design more “crisp”. The production input is what weight of fish you would like to produce in a given amount of time. There is a tick box to the right that will convert all the inputs and results to either imperial or metric. You can put in any number you like but be realistic as this calculator is not designed for very large systems but will work just fine for boutique/hobby size farms. The time setting is in days.  This refers to the production input above and how long you want to take to grow that amount of fish.  Generally this will be set to a year (365) but move the slider about to see how it changes the entire design. The feed conversion ratio (FCR) is usually a large assumption about how much feed it will take to grow 1kg or lb of fish.  Normally I would set this to 1.5 to allow a bit of breathing room in the design.  This will affect all of the output design requirements. The daily feed rate is the amount of feed per day as a percentage of the body weight of the fish.  This varies for species and age of the fish.  Overall you may be looking at achieving 1.2% per day.  However as young fingerlings arrive, you may be feeding up to 10% of their body weight per day. Feed protein is simply the amount of protein in the fish feed you are using.  This changes with species type (omnivorous, carnivorous herbivorous) and their age.  Generally fish will start at a higher protein percentage when young and reduce to the lower level of protein as they grow. Fish assimilation is basically how much of the feed the fish will use for their somatic growth and energy needs.  This is a very flexible number and changes with condition, feed type and management.  It can vary significantly from species to species but in most cases you can estimate 36% in this setting. Fish and biological oxygen demand is related to the amount of feed put into the system and how much oxygen is needed to metabolize or catabolize that feed.  In most cases it is safe to assume 0.5kg for each.  However in a well filtered (micron) system the biological oxygen demand can be as low as 0.25, but in poorly filtered system the biological oxygen demand can be as high as 1kg. Feed timing is over what period you are feeding the fish.  For example if you are feeding in the morning then again in the evening, manually, you may set this to 12 or 16 hours.  Automatic feeders operating all day and night can be set to 24 hours. The oxygen transfer rate is a known transfer rate of oxygen per kw of power for aerated systems at 20c/68f temperature and 0mg/L of oxygen in the water.  Adjustments further down adjust that rate for field or culture conditions.  The slider has preset limits of 1kg to 1.6kg. Water temperature is the culture temper for the fish you plan to grow.  There is no allowance for season changes.  If you are working with variable temperatures, set this to the highest it will get.  If controlled system temperature, set it to that temperature suited to the species you are growing. Dissolved oxygen level is the minimum amount of oxygen you require for the fish health in the culture tanks.  We have not accounted for the biological filter as it will be lower than the fish needs.  In most cases for warm water species this will be above 5mg/L for cold water species it will be 6 or 7mg/L.  Keep an eye on the blower size in the results column.  If you set this too high your blower will be huge. The air stone flow rate is the manufacturers air flow rating for your selected air stone diffuser.  This setting will affect the amount of air flow and amount of air stones required.  Always better to choose a larger air stone to reduce the amount you have in the system. Media surface area is the specific surface area (SSA) of the bio filter media of your choice.  In this scenario we are only using defining a moving bed bio reactor (MBBR).  Later calculators will look at the various types for design with some combinations.  Your supplier of the media will be able to let you know what the surface area of their media is. Ammonia removal rate is the amount of total ammonia nitrogen (TAN) removed by the bio filter per square meter of surface area per day.  This is a very wide number but generally, 0.3 to 0.5 grams per day per m2 works well. The residual ammonia is the amount of ammonia that will be in the system at any given point of time.  Keep an eye on the Un-ionized Ammonia level and pumping rates in the results column.  The more ammonia left in the system pumping rates will increase.  You want to be sure the Un-ionized ammonia is below 0.02mg/L.  Above this is toxic to most species.  You will not be able to set this to 0 simply because ammonia is being produced constantly.  Your basic test kits may read zero but they are not capable of reading lower than 1mg/L of TAN.  So dont be fooled by a 0 ammonia reading on your colormetric test kits. System pH is where you will keep the pH of the system for the species you plan to grow.  You will note as you increase this the un-ionized ammonia will increase.  It will also increase as you increase the water temperature.  Set this at the highest point your system will run while keeping an eye on the un-ionized ammonia. Biofilter efficiency is a soft number.  In most cases moving bed bio filters will be close to 100% but setting this to 90% is a good place to be if you have micron filtration.  Often over the life of a filter, if the solids are not removed its efficiency is reduced.  In the case of poorly filtered systems, this may be as low as 50%. The biofilter retention time gives the bacteria enough contact with the influent water to process the ammonia on a single pass.  However sometimes this is not possible due to space constraints.  Low retention times (<5minutes) may mean you will not remove the ammonia on one pass but your biofilter will be smaller.  In that case a second bypass across the biofilter may be needed.  Generally 10 minutes is a good target. The stocking density is the maximum weight of all the fish in the system per unit volume of water.  The slider has set maximum limits that are suitable to aerated systems.  Generally over this maximum oxygen is required.  If you are starting out, you can set this high, that will increase the tank size, but start your first year with half of that weight and if you are successful increase it the following season.  Commercial systems you will want to determine the best option for your farm and husbandry skill. Please provide your feedback and questions below. Regards Paul…