Small vs. Big W/C's

  1. Adoinc Initiate Member

    (Ok, so let me explain. If I were to do 7 5% water changes (35% in total) would it be better than doing one large 35% w/c at the end of the week?

    I want to know your opinions and why you feel that way.

    I know in some cases frequent is better, but it seems like 5% everyday isn't doing much compared to 35% once a week.
     
  2. Marie1 Well Known Member Member

    I do at least 50% once a week. Sometimes more if I'm not paying attention to the siphon. The fish don't have any negative effects from a single larger water change. Look at people who breed and grow out discus. They are known to do 100% water changes daily. Granted, it takes 2 water changes to change out 100% of the water, but none the less. Large water changes are fine. And I would rather do it once a week, than every day.
     

  3. Blueszz Well Known Member Member

    When you take out twice 50% and fill the tank in between you actually do a 75% water change, not a 100% because the second time your 50% is 25% old and 25% new water.

    I think the same applies for 7 x 5% water changes because you always take out some from the days before.
    My math skills are horrible so I might be wrong :)
     

  4. stargazerwolf Member Member

    I would think it'd make more sense to do say a 25% water change twice a week than a big 50% water change once a week, id just think it would mess with the fish more...but I generally only do a 10% twice a week on each of my 10 gallons because it is just shrimp and snails...However I'm not sure there is a big difference...I think it'd be pointless to do 5% every day, I don't think it would do anything really...but I could be wrong.
     

  5. mopa Member Member

    I usually do a 25% water change each week. However I only vacuum half the tank each time.
     
  6. Rivieraneo Moderator Moderator Member

    Hi Adoinc, the only time I would suggest small water changes is if your water source had an extreme issue with undissolved gasses where CO2 would need to be degassed from your water to match the PH in your tank and you had no ability to age large quantities of water, if you had a tank set up per the walstad method, or had fish which were stressed due to the water change. Personally, I do one large water change per week in all my tanks at a rate of 75%. I do this because my goldfish went through a short fish in cycle and large water changes had no effect on them. Both my bettas and flowerhorns love fresh water and I have had no issues with them either.

    Keep in mind, my tanks are a mixture of bare bottom, planted, planted with gravel, planted with bare bottom, so I also conduct large water changes to manage nitrate build up in my tank. My testing shows my planted tanks with low nitrates at around 10PPM even after a week of no water change, but i conduct water changes regardless.