I updated my chart the other day. I decided to round the plateau time line to the .000x decimal, so now the time line is shorter. I also added an osmotic stress factor which is pretty close to your %'s.
I updated the tds calculator a little too, the new version is here-
Keith, do you think you could double check the accuracy of this calculator. I want to start writting a web version of it, but I want to be sure it's not faulty. You're the 1st mathmatician I've run into that's also fish savy, so I'd like to know your thoughts. I have some other programs I'd like your opinion on as well, if your interested.
1. Your columns are labeled, for example "Next week pollutant %". It should be "Next week pollutant % change", since you just list the % change.
2. When I first did the calculation, my results did not match yours until I realized that my first water change corresponded to your second water change. That is, I started at time zero with a given pollution level and then after a time interval I did a water change. You have started at time zero, done an immediate water change, and then after the time interval done another water change. There is nothing wrong with your method, but to easily implement the idea in number 3 below, it might be worth it to switch methods.
3. For TDS and any other pollutant that is in your aquarium and also in your input water, your calculator is very good. But for pollutants like nitrates that accumulate in the water and are not in the input water (ideally), a small change in your formulas will give improved results. The idea is to add an input pollution rate (which we can measure by tracking with water tests).
4. I have a formula for computing the plateau (rather than iterating many times). I also have a formula for computing how long it takes to get within .1% of the plateau (or whatever tolerance is best).
5. The tables that I put at the beginning of this thread, can be easily added to your calculator since it uses all of the same types of data and information.
I will get the methods written down to do 3, 4, and 5 above so that you can see just what I mean. It just involves geometric series and algebra.
If you can write a web based calculator it would be really great.
I have earlier and later versions of the TDS calculator, all being a little bit different. I'm not sure why the functions are the way they are. I should of taken notes. I was working on a much more advanced version that has inputs and estimations for fish density, food consumption, plants, lighting, nitrates/phosphates. I haven't worked on it since last year though.
The food consumption part of the calculator has a drop down menu of foods to choose from. The calculator will estimate how long each food container will last based on feeding frequency, portion size, and container size. But mainly, it estimates the amount of ammonia (nitrates) and phosphates each food will produce based on the protein % and phosphate % of the food. I'm not sure where I left off on this program though. I really need to start taking notes. Usually I work on a program based on necessity, but now I'm also taking classes for programming. It seems like for everything new I learn, something old is forgotten.
I need to get me an intern.
I also have a spreadsheet that does the above, but it is not formatted as nicely as chefkeith's spreadsheet. I can make it available, but I am hoping that chefkeith will make the changes to add accumulating pollution in the tank to his spreadsheet. This would make it so that we could take nitrate measurements over a time period and get the value of r above. We can also measure the nitrates in the input water (hopefully zero) and then use the spreadsheet to see how much water it is necessary to change, per the time period of your choice, to keep the pollution level from rising.
Comment: The above formulas work fine for parts of days. For example if m = the number of days is set to 1/(24*60*60) then it corresponds to a water change every second, which is a very good approximation of how to do a continuous drip. I have compared the actual value to this approximation and it is so close that I think there is no need to use the actual value.
I would love an automatic system but if you have multiple tanks in multiple rooms, it would be a complex plumbing fete. Just figuring out and installing the plumbing for our system was a chore and a half.
Perhaps someone has worked this out and can give some recommendations?
Since I wanted to check everything for accuracy and see that the formulas work, I took the time to add the accumulating pollution option to chefkeith's spreadsheet. Chefkeith, I hope that you do not mind that I have done this. Your spreadsheet is so nicely set up, and works so well, that I was anxious to add this extra pollution accumulation factor to see how it all works. If the accumulating pollution is set to 0, then the results are the same as they were before I made any changes. You may download the spreadsheet at
http://people.consolidated.net/kwolcott ... Wizard.xls
I have turned protection on (tools menu of excel) so that I don't accidentally erase any of the cells which have formulas. The input cells are, of course not protected so that you can put any initial conditions in that you desire. There is no password on the protection, so you may turn off the protection and change any formulas that you wish (for anyone that may have other quantities that they wish to compute).
Remark: If you play with the wizard a bit, you will see that the frequency and % water change that you do has hard to predict effects on the long term results. Some choices may seem reasonable, but over time have a high pollution plateau, and thus are not really very good.
I also added a small section near the bottom that incorporates the two tables that I posted earlier. Thus, for a given water change % and frequency, you can see the required % water change for other frequencies that have the same effect on the amount of pollution. It also shows how much water is used per day for each water change frequency.
If you set the water change frequency at 1 second, it is effectively continuous, so you can see the rate that a continuous drip needs to be in order to be effective and how it compares in water usage to other frequency choices.
You can also enter a pollution level goal and it will tell you the % water change that is necessary to achieve that goal.
It opens the door for other things.
I think the Fish food calculator I have might help estimate the input pollution.
It will calculate the ppm of fish food added and estimate the ammonia it will produce.
http://www.geocities.com/chefkeithallen ... wizard.xls
It still needs lots of work on it's food index and I should research the protein -->ammonia relationship more, so that I can validate the accuracy of the ammonia %'s I calculated.
My head has been a mess lately though. I'm recovering from some shoulder/back injuries right now and the med's I'm taking are making me dumber by the minute. I'll be taking it easy for few weeks.
Once again great stuff. Can't wait to see what you do next.
I have taken a look at your fish food calculator. I really like your idea that essentially all input pollution comes from the food that we put in the tank (whether it is eaten or not) so that the amount of ammonia, nitrite, nitrate, etc. can be estimated. Yes, I agree that this could help get good values (along with using water tests to measure actual values) for the input pollution rate. I will study what you have done. Right now I don't understand any of it, but I look forward to learning how it all works.
I meant to thank you, and to say before that you have taught me some new things about spread sheets. I knew some, but you did a number of things in your spread sheet that I had not seen before, but that are very useful.
Sorry to hear about your shoulder/back. I hope that you recover soon.
I now see why my nitrates have doubled over the past few months. My "P" or nitrates were between 30-40 before my last water change. The food calculator estimated that the fish produced about 3.2 ppm of "P" or ammonia--->Nitrate to my tanks daily. The result is that I'd have to do 25% water changes every other day to get the P down to the goal of 20 ppm.
I could add a 95g sump so that I'll have more water volume in the system. The added volume would decrease the "P" to 2.3 ppm per day. Then I'd only have to do 2- 20% water changes per week to reach my goal of 20 ppm.
I need to get this sump running ASAP. I just need to plumb it.
I Googled "aquarium continuous drip water change" to try to get some more ideas on how to get my sump / reservoir hooked up and Your thread, THIS THREAD is #1 on Google.
I have more Good news too. I got my new water change system finished and working Today. The Water Change Wizard helped me decide on what exchange rate my fish needed. What I built is a Semi-Automatic Intermittent Water Drip System.
The 95g sump is the water change reservoir. The Reservoir will need to filled with freshwater every 3 to 4 days. The pump in the reservoir is on a timer. I'll probably set the timer to run for 8 - 12 hours per day. I only want this running while I'm home so that I can supervise this somewhat. The output rate from the pump is variable. I can drip it in slowly or spray it in for a quicker water change. Right now the drip rate is about 2.37 gallons per hour, or 28.5 gallons over a 12/24 hour period, or 11.4% of the tank daily.
The output from the main tanks is siphoned off to an external overflow that has a python hose going to a facuet/sink. The overflow has some bypass valves so that I can use the Python hose to fill up the Reservior also.
I'll take pics of everything and post them on a new thread in a few days.
BTW, on the water change wizard in the frequency section, if you enter a "T" for every 12 hours, you'll discover that the output formula needs to be changed from 1/12 to 1/2.
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