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water changes (+ your input)


13 Aug 2008
Surrey, UK
right guys, im fed up with doing w/c's every week on my 2 larger tanks. one is non co2, no ferts and only has 12 rasboras brigittae and soe cherry shrimp. my question is, do i still need to do a w/c every week? or can i get away with a longer time?

my second tank is my planted tank, with pressurized co2, ferts etc. can i get away with doing a 50% change every 2 weeks or is that pushing it?

for people with tanks ranging from 120L to 300L, can i have your help, how often do you do a w/c. do you have co2 ferts etc.



Expert/Global Moderator
11 Jul 2007
Chicago, USA
Well, water change requirements have nothing to do with the size of the tank. Water change only has to do with growth rates and waste production. So you'll need to reprogram your thinking and approach it from this standpoint. The growth rates and waste production are strongly correlated to the level of nutrients and the level of Carbon being input into the system. For a non carbon enriched tank with sufficient plant mass, there is no need to do water changes at all. So that's easy.

For enriched tanks if you want to reduce the need for water changes then you'll want to reduce the growth rates/waste production by reducing the appropriate combinations of nutrient levels, injection rate and light.



21 Jun 2009
I looked at ways of making water changes easier and bought the following :

1. 2 x Wheelie bins of sufficent size, although 1 will do as the second one is for storing waste EI water for house plants. Any contianer of sufficent volume on wheels will do or even a big plastic dustbin if your happy to " drag " it.
2. A pump capable of pumping water vertically 2 meters , got a little ehiem but even a knock of would do i guess.
3. Enough hosing with a plastic crook to hang over the tanks edge.

It dramatically cut down the amount of work needed especially when it came to filling the tank. I fill the wheelie bin in the kitchen with the sumberged pump at the bottom, add the dechlorination chemicals once a little water has been added and then fill it up to the required amount ( thus ensuring good distribution ). If dosing EI as I am I also add the ferts to the bin before filling it ( distribution ) . Then its a case of wheeling the bin about the house and filling the tanks. You can even pull up the pump to certain levels in the tank so that it runs out of water not overfilling the tank if you have to for some reason leave the room. I have found water changes a much more pleasant experience since then.

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