I need help ending a debate on water changes!
- Thread starter Megatron
- Start date
Saltwater you don't have to do as frequent WCs as freshwater because many times a bacteria will establish itself in SW tanks to consume the nitrates. I responded to this a while ago but this is what I do now. Juvi discus tanks get 75% wcs every other or every day, the adult discus tanks 75% 3 times a week, everything else will get at least a 75% change each week. You really can't do too many WCs, clean water will help any fish out.
I as a general rule do water changes every week when I clean my scrubber and it is usually about 30%. On my other tanks this can vary ,but I do have to say that the nitrates in my main tank are less than 0.2ppm (can not measure lower than this), and the tap water's nitrates is at a level of 10-15ppm. I agree that there are other wastes and hormones that can only be taken out by water changes, but for getting nitrates down to an unmeasurable level , algae scrubbers have little competion.
Ok, this is what I've wondered about for a while.
In SW tanks there are organisms that apparently consume the nitrates. But what about the other TDS? Every single person, I have met, that keeps a SW tank, does very little water changes compared to most of the "serious" FW tank keepers. Ranging from a coworker that changes 20% a month to my father-in-law that only does a water change(not sure how much) around every 4 months.
Is this bad for SW tanks? Or is there something that vastly different between FW and SW that makes water changes not as important?
In SW tanks there are organisms that apparently consume the nitrates. But what about the other TDS? Every single person, I have met, that keeps a SW tank, does very little water changes compared to most of the "serious" FW tank keepers. Ranging from a coworker that changes 20% a month to my father-in-law that only does a water change(not sure how much) around every 4 months.
Is this bad for SW tanks? Or is there something that vastly different between FW and SW that makes water changes not as important?
There are a lot of other things in the SW tanks that will help control the TDS as well. Corals and inverts use a lot of them up.
When I had my tanks all set up and running I ended up doing weekly water changes of about 30 to40% each week. I never tested for nitrates at that time.
I arrived at that amount because it was pretty much what was removed from my goldfish tank each week when I vaccuumed the gravel. Then I just did the same amount for the whiltecloud tank and the betta tank. These all had filters and plants. No additives for the plants or anything.
I didn't, (still don't) have a python. I just used a regular siphon/water vac.
I actually kind of liked it. Each week on a Tuesday I'd do all the tanks and use the old water to water my houseplants. The house plants Thrived! and the fish seemed to do fine also. the whiteclouds are still alive ...the original ones are over 5 yrs old now!. The last betta died last year. (I gave them in their tanks, to my father when I moved. he kept up the weekly water changes)
I arrived at that amount because it was pretty much what was removed from my goldfish tank each week when I vaccuumed the gravel. Then I just did the same amount for the whiltecloud tank and the betta tank. These all had filters and plants. No additives for the plants or anything.
I didn't, (still don't) have a python. I just used a regular siphon/water vac.
I actually kind of liked it. Each week on a Tuesday I'd do all the tanks and use the old water to water my houseplants. The house plants Thrived! and the fish seemed to do fine also. the whiteclouds are still alive ...the original ones are over 5 yrs old now!. The last betta died last year. (I gave them in their tanks, to my father when I moved. he kept up the weekly water changes)
happychem said:
There seems to be an irony in all this. If you do a 50% water change then you are dramatically altering the water chemistry with every water change. As your calculations show:
With every 50% water change you've altered some of the water's chemistry by 50%. Ph and temp may be the same or very close to it, but other factors have changed dramatically.
But water parameters change by only 10% with every change; the very thing you said was good in the previous paragragh.
I wonder if there are better solutions than large water changes. What if we attempt to remove that waste by other means like excellent mechanical filtration that is cleaned two or three times a week combined with a very shallow or even no substrate to collect and store a substantial portion of that waste? What we might end up with is a tank of identical bioload that leaves only 10 units of waste to be dealt with by water changes. The other 90 units are removed by a combination of daily 2 minute nettings of the bare tank bottom and regular cleaning of the mechanical filters to take the waste out before it is broken down into solution. Under this scenario 10% water changes result in a max waste level of 100 units, precisely half of the level they'd be at doing 50% changes and subjects the fish to a weekly 10% alteration in water parameters instead of a 50% alteration.
Percentages are tricky things, ultimately they're meaningless if you don't put them into perspective. What's 50% of 200? What's 10% of 1000?
This isn's an accident, the tank stabilizes as the quotient of weekly input to fraction of water changed. So the change that the fish encounter each week after the tank has stabilized is the same in terms of units.
However, the water in the 50% regime is 5 times closer to the source than the smaller regime and is maintained at a lower level of contaminants. Both are desireable.
But this example is just to help explain how chemicals behave in your water. Ultimately this ties in very nicely with the "keep NO3 below X ppm" approach. If each week NO3 in your tank increased by 5ppm, then 50% weeklies would leave you with 10ppm NO3. If that's your threshold, great, if you think that NO3 should be below 20ppm, then you can safely scale back to 30% and still be below your threshold. Dig?
This isn's an accident, the tank stabilizes as the quotient of weekly input to fraction of water changed. So the change that the fish encounter each week after the tank has stabilized is the same in terms of units.
However, the water in the 50% regime is 5 times closer to the source than the smaller regime and is maintained at a lower level of contaminants. Both are desireable.
But this example is just to help explain how chemicals behave in your water. Ultimately this ties in very nicely with the "keep NO3 below X ppm" approach. If each week NO3 in your tank increased by 5ppm, then 50% weeklies would leave you with 10ppm NO3. If that's your threshold, great, if you think that NO3 should be below 20ppm, then you can safely scale back to 30% and still be below your threshold. Dig?
Increasing the frequency of water changes has an equally positive affect on water parameters.
If we reduce our disolved waste by cleaning our our filters before the waste disolves into solution and we net the waste daily from the bottom of the tank we can dramatically reduce our weekly waste load. In the last example we assumed it was a 90% reduction, leaving only 10 units per week instead of 100 units to be removed by water changes. If we switch to changing water twice per week instead of once per week the accumilated waste gets cut in half from 10 units to 5. The stabilized waste level through time with 10% water changes becomes 50 units (5/.1=50), half of the previous level.
Interesting stuff.
If we reduce our disolved waste by cleaning our our filters before the waste disolves into solution and we net the waste daily from the bottom of the tank we can dramatically reduce our weekly waste load. In the last example we assumed it was a 90% reduction, leaving only 10 units per week instead of 100 units to be removed by water changes. If we switch to changing water twice per week instead of once per week the accumilated waste gets cut in half from 10 units to 5. The stabilized waste level through time with 10% water changes becomes 50 units (5/.1=50), half of the previous level.
Interesting stuff.
An interesting scenario. It works well with stuff like fecal matter and scales, but less well for ammonia derived nitrate and fish hormones, released through the gills.
Certainly frequent mechanical filter cleaning is a good notion. Ditto the frequent water changes. Two 30% changes weekly is the same as a single 50%, chemistry-wise, but with a smaller percent oscillation in TDS.
Certainly frequent mechanical filter cleaning is a good notion. Ditto the frequent water changes. Two 30% changes weekly is the same as a single 50%, chemistry-wise, but with a smaller percent oscillation in TDS.
