Tropical Fish Forum

Tropical Fish Keeping Help and Advice => Fishtank Filtration and Cycling => Topic started by: ColinB on March 07, 2014, 12:26:13 PM

Title: Water Change calculator
Post by: ColinB on March 07, 2014, 12:26:13 PM

Here's a little something I put together one rainy afternoon about how much 'old' water is left after a number of water changes. i.e. Two 50% water changes doesn't equal 100% of the water changed as the second of the water changes includes some of the previous 'new' water. So two 50% water changes leaves 25% of the water unchanged.

The Table attached has a highlighted square to aid an explanation. 

The number of water changes is Column A; in this case 4

The percentage of water changed is in Row 1; in this case 25%

So if you do four 25% water changes then there is still 32% of 'old' water left in the tank.

This may be of some interest to people..... but it whiled away my coffee break.... so I'm happy! :) <-- See?

Title: Re: Water Change calculator
Post by: fishcake76 on March 07, 2014, 02:25:47 PM

This is very useful, I'm thinking!!!!

Bit confoosled though,  what is row 2??  ???

I is not very bright!!!!

FC

Title: Re: Water Change calculator
Post by: ColinB on March 07, 2014, 02:44:24 PM

Row 2 is 100%. In Excel that row is changeable to the actual tank volume and the table recalculates everything into litres. But as that won't work as a posted reference I put 100litres in so the table works as a percentage figure.

I'm afraid you'll have to do the maths yourself...... or you could tell me your tank volume and I'll post a table specific for your set-up so all the figures are in litres.

Hey look..... a fishy thing to add to the post.... :fishy1:

Title: Re: Water Change calculator
Post by: fishcake76 on March 07, 2014, 02:56:29 PM

My tank is 18 inches by 10 inches so is classed as 30 litres but actually holds 26 litres. If you could do a table for me that would be very helpful. Maths is not my strong point!!

thanks!!

FC :)

Title: Re: Water Change calculator
Post by: ColinB on March 07, 2014, 03:20:37 PM

No probs - I'll do it at my next coffee break...... which is very soon. I drink a lot of coffee ;D

Title: Re: Water Change calculator
Post by: ColinB on March 07, 2014, 03:55:05 PM

Ta-daa:

So, for example, if you did three 10litre water changes to your tank, you would still have 6litres of the 'old' water left in the tank.

Title: Re: Water Change calculator
Post by: fishcake76 on March 10, 2014, 03:39:13 PM

Thanks Colin!!

 :)

FC

Title: Re: Water Change calculator
Post by: SteveS on March 10, 2014, 04:55:11 PM

Here's a different one. Download to your PC and open it in your web browser.

Title: Re: Water Change calculator
Post by: SteveS on March 10, 2014, 08:30:01 PM

At the time I posted this it was really what I said it was, honest :). It still is, but you should waft it through a virus scan before you open it!