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Fish Tank Water Testing

  We are well into week three of our nitrogen cycle with our 20kg of Jade Perch and now it is getting really colourful using the API Fresh Water Master colorimetric test kit.  As you can see from the reading above we have all three, ammonia, nitrite and nitrate at the My Fish Farm camp and they are here with gusto.  Last week we tested the API against our Hanna Photometer to see what the differences are and so we did it again this week and these are the results. [heading] Fish tank water testing [/heading] Ammonia The Hanna meter reads 3.30mg/L of Ammonia Nitrogen (NH3-N) which we will need to multiply by 1.216 go get the Ammonia reading (NH3) we are looking to match the API test kit.   Now we have a reading of 4.01mg/L The colorimetric API test kit reads around 4mg/L. Given the water temperature is a cool 15c and will not reach much higher than 17c today and a pH of 7.4 we have free ammonia (the toxic stuff) at 0.38 which is above the recommended 0.20 where for a short period it can be tolerated by the fish.  This recent high reading will be due to me being lazy and adjusting the feeder yesterday over the fish tank instead of removing it for adjustment which resulted in the fish getting a bit more feed than was needed. As that level is not ideal the feeder has been turned off for today. Nitrite The nitrite is an entirely different reading.  The Hanna unit reads at 0.38mg/L which is Nitrite Nitrogen (NO2-N) and because the API test kit reads total Nitrite Ion (NO-2) we have to multiply that 0.38 by 3.29 to give us the Hanna reading of 1.25mg/L.  I know it is confusing.  The API test kit roughly reads 1 to 2mg/L which is a good indicator of where we are at.  When using the indicator tests, if you think it is somewhere between assume the worst and go for the higher number, in this case 2mg/L. Some may be thinking “Paul you have to change the water out quickly man, far out!!”.  Not the case, sure we are what I would call the “tipping point” for cycling this system where the fish will either die or we will make it through safely over the next week. One concern with the weather currently is this cold front moving over us, this sudden drop in temperature will slow the bacteria down and often nitrite will continue to rise.  This is especially evident in sudden changes in season from summer where you are feeding hard, to winter when the bacteria a suddenly exposed to cold conditions (they don’t like that much) and it takes them time to acclimate to the change.  This is a good time to be sure your solids filters, be they purpose built of grow beds are free from organic waste build up or quite possibly you will suddenly have readings of elevated nitrite and wonder what happened… Lucky for our little Jade Perch, the system has already been treated with 7kg of salt when it was started and it has been having its daily dose of 40ml of hydrochloric acid.  The initial salt treatment was for the stress the fish will have suffered when they where transported, then handled into their new home with us.  The hydrochloric acid is simply battling the super high pH and alkalinity of the tap water here.  Both of which provide chloride to protect the fish from the toxicity of the nitrite and lowering the pH to keep the Ammonia toxicity level low.  So I think we are safe… Nitrate Our good friend Nitrate is well and truly in the system and it is an indication the nitrogen cycle is in its last stage and we can expect the Nitrite and Ammonia to start falling over the next week or two. The Nitrate reading again is the Nitrate Nitrogen so we have to multiply this reading by 4.43 to match the API test kit of  5mg/L.  This gives the Hanna reading 3.31mg/L so they are not far from each other and really it matters not if you mess the Nitrate reading up. Nitrate is often called “harmless” and while it is the food we are looking for to feed our plants in My Veggie Patch, at high levels (above 100mg/L) may cause problems.  High levels of Nitrate will contribute to the Nitrite production slightly in any system but more so in anoxic (low oxygen, high nitrogen) environments like packed media filters or grow beds. So the next week or two will sort out the wheat from the chaff.  This is the critical point in any system cycling for the first time and it is easy to make a mistake, like not taking the auto fish feeder out to adjust it…  Lessons learned or reminded. Regards Paul[/private]…

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