Importance of changing filter cartridges?

Discussion in 'Cleaning and Maintenance' started by lp89, Nov 25, 2012.

  1. lp89Valued MemberMember

    I need to start by making an embarrassing confession that has lead me to this question.
    I recently tore down a 3 year old 10g, and set up a new 29g tank. Both aquariums used HOB power filters, with replaceable filter cartridges. The manufacturer suggests changing the filter cartridge every 2-4 weeks.
    However, in the entire 3 years that my 10g was set up, I never ONCE changed the cartridge (Yikeees! :;smack horrible fish-keeper, horrible fish-keeper....).
    Years ago when I set up my 10g tank, I followed advise to "never change the filter media" and mistakenly took this to mean the filter cartridge. Every few water changes I would removed the bio-fiber and the cartridge and rinse them in tank water, but always plopped them both back inside the filter box. I NEVER replaced the cartridge. I only recently realized my mistake when I purchased my new 29g and started reading about the nitrogen cycle again.

    The weird thing, is that even with the really old (and ineffective cartridge, I assume?), my tank seemed pretty healthy. I did 10% weekly water changes, and water tests always showed no ammonia/nitrite. My plants grew well, and I never had any strange fish deaths.

    I guess I am struggling to understand the REASON this cartridge must be replaced so often.
    -What exactly do those little pieces of carbon inside the cartridge do for my tank? The one in my 10g was obviously doing nothing, but was it harming my fish?
    -Are there differing opinions about how often the cartridges really need to be changed?
    -Did I just get VERY lucky? :p
    Last edited: Nov 25, 2012
  2. ayladWell Known MemberMember

    You did right with the 10gal, actually.

    Carbon stops being effective after about 3-4 weeks, but may not do any harm by staying in the tank.

    Changing the filter cartridge gets rid of the beneficial bacteria that you need to maintain the cycle.

    Filter companies (and the fish store employees) generally tell you to replace the filter media often. They would. You have to pay for new ones. Ignore them and save your money. ;)

    PS. as far as replacing carbon when it becomes ineffective, some of us (myself included) never use it anyway. :)
  3. JayseeFishlore LegendMember

    I don't use carbon either, and I always find it funny when people talk about how carbon leaches stuff back into the water - since the "stuff" is never removed from my tank in the first place. There is no chemical reaction that takes place so what goes in is what comes out. But yeah, the carbon becomes useless as chemical media, but it does not become totally useless - bacteria grows on it, like anything else.

    Because I don't use carbon, I haven't replaced anything in my filters in years, and won't for many years. Most cartridges aren't the best quality, so I think you got lucky keeping the same one all that time. But as far as the fish are concerned - no luck at all. You got good advice and followed it.
  4. Orion5Well Known MemberMember

    As was stated here, you were right with your 10 gallon tank. You had a wonderful bacterial population cultivated which led to your success. :)

    I share the opinions of the other responders here and their view of carbon in a filter. I only used it to clear out medications after they had their run. That's why it's important to know that carbon will leach out what it took in after a few weeks if you use it to filter meds from a tank-- you don't want the medications constantly circulating in the tank, so taking out the carbon and disposing of it is the way you deal with that.

    Fish store employees will often cringe if you tell them you're not using carbon in your filter, especially if it's just the little fish section of a pet shop. Aylad is right, they want you to buy more stuff, but they also may not keep fish in any serious way and therefore are just going with what the supplier's book tells them to- which is obviously geared toward making more sales. Complete lack of knowledge on their part.

    Best of luck! :)
  5. ayladWell Known MemberMember

    Because you're getting a one-sided set of responses on the topic, I'll switch sides briefly and mention that many members here LOVE using carbon and recommend it to anyone who'll listen. :)

    I don't know of any hard, conclusive evidence for or against using it on a regular basis, and I've heard people argue convincingly on both sides of the "does it release toxins back into the tank" question. I personally don't use it, but I'm not opposed to it either.
  6. JayseeFishlore LegendMember

    That's one of those things for you to figure out on your own - the importance of carbon.
  7. lp89Valued MemberMember

    Wow, I really wasn't expecting such favorable response! I really thought I had committed a huge fishy crime! haha

    I never needed to medicate the 10g, so I wouldn't know if the carbon was releasing toxins back into my tank that it had cleaned out. I guess it never got to do it's job..

    As long as reusing the same cartridge wont hurt my fish, I think I'll try to save my money! :)

    One more quick question: Is it possible that carbon had an effect on the PH level of my tank?

    My tap water has a PH of 7.6
    New 29g is 7.4
    Old 10g was 6.8

    I'm wondering why there is such a difference, could carbon(or lack of) be a possible reason?