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Biofiltration and Water Temperature

Water temperature plays a very important role in any aquatic system.  Temperature tells us many things about the activity in our aquaculture or integrated aquaculture set ups.  While the local climate tells us what fish we can grow and how it affects them, temperature changes can also alter our biological or bacterial activity.  In this article we will continue our conversation from Feeding Fish – Design Consideration and touch on the biofiltration and water temperature. [heading] Biofiltration and Water Temperature Effects [/heading] We will reference the surface area required for different feeds per day from the previous article and use it to see what roll temperature changes have in selecting how much media we require in the table below. The table above reflects the surface area required for different protein levels in feed applied at different rates through out the day.   It is based on feeding 25kg of fish at 1% per day.  From that table we will use the same feed rates at 30% protein and see how the temperatures will change the size of the surface area required at different temperatures for complete TAN (Total Ammonia Nitrogen) removal or nitrification. We have not yet taken into account the Ammonification, the breakdown of organic nitrogen from leaving feed and fish wastes in the system.  We will look at how these affect your system in a later article. Bacteria can acclimate to wide range of temperatures degrees Celsius to where our fish will either not survive or will not grow.  Below 20c and above 32c the nitrification process will be limited.  Also sudden temperature changes, especially weather driven cold fronts, will slow our little bugs down. The easiest way for me to explain what these temperature changes do to your system and how it should be considered when sizing your system is through yet another table….  Saves you doing the math. As I said earlier, above 32c and below 10c bacterial activity changes dramatically however I only have “loose” numbers for this so the red indicates and unknown quantity and most fish we grow will not be too happy outside those temperatures anyway. In this table we have taken the surface area required for 250 grams of 30% protein feed and we assume a 100% nitrification rate at 20 degrees Celsius.  Using the green column you can see the changes up and down 10c will have a 27% increase or reduction in bacterial activity.[note style=”” bg=”” border=”” bordercolor=”{{bordercolor}}” color=””] What ever bio filtration you think you need add 30% [/note] For example, if we use this feed and feed 2 times per day (125 grams of feed per feed), at 20c or 68f we need approximately 45m2 or 485f2.  (to convert M2 to F2 multiply the M2 x 10.764).  if we live in an area, like my home, where water temperatures can drop to 10c we will be better to increase our bio surface area by 27% to 63m2 or 678f2. So upsize your bio filtration by 30% is easier to be sure we have enough surface area for those crispy moments.  Call it a “stuff up factor” if you like. We also know that as the temperature decreases, fish metabolism also decreases, so we feed less. Even to a point with some species don’t eat at all and produce very little ammonia.  This is less important for warm water systems but growing a cold water species, like trout who eat very well at those low temperatures, it best to plan ahead. As they say, in summer, plan for winter.  In winter plan for summer. Regards Paul…

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