I lately resolved into feeding every other day, for my fish didn't seem to digest all I gave them in just one day.
Now i wanted to know if my 50 % waterchange weekly was actually nescecary,for a friend of mine said he thought it was bogus, all the waterchanges.(He's own a huge koipond)
Now last week i was sick at home and couldn't bother to do maintenance.
So, I took the opportunity and tested for nitrates,after skipping one week of wc, 40+
Now that kinda proves that the religious waterchange scheme is back in action and there's no way I can down those wc.
Even if it's a big tank, having some many feet of fish is heavy on the bioload indeed, and Nitates will skylevel very fast!
Did the usual 50%wc today and just tested Nitrate 10.Just as I like it.

On the other hand i have my 90Gl community and pleco tank.
I cleaned the filters 3 weeks ago and skipped wc last week aswell.
Now i tested and got a Nitate of 5.
I was doing allmost the same wc scheme on that tank as well, 50% weekly, but after testing i decided that that tank is gonna need less frequent waterchanges.
It's lightly stocked and heavily filtered, so that figures.
So I was looking to save some time, and I now I found it in one of the other tanks!

My O behaved like a sissy during wc today and was sulking like a baby.



His small tankmate was less frightened, and has survived for over a month now.
Thinks he's a Silver Dollar now!

Well I generally change the water according to my water tests.

At the moment while the Oscars are still babies, this only needs to happen about every 3 weeks, but can happen once a month safely.

My Malawi tank on the other hand, which is pretty well stocked gets a bi-weekly water change without issues.

Naturally a weekly water change can't do any harm, but often I find it can be overkill depending on the size of the fish and the size of the tank, and could be counterproductive (with regards to stressing the fish).

if you have a lot of floating plants inside your tank, it will give you buffer
time for water change, but definitely, it will still be based with your stocking.

i think ponds and tanks are very different in a way. yes the fish are looked after in the same manor but you just don't view the bottom of a pond like a tank. i started my fish keeping with a very large pond stocked with Koi. i ran a large filter that was cleaned and maintained daily. the pond was heavily planted with bottom weed/lilly's/small shallow water plants and it had a very heavy layer of silt or mud on the bottom. i changed half a day water every 6 months. I couldn't tell you how many gallons that was but the tap was high presser and on full. i never had water changes like the tank but for half the yr i couldn't see the bottom, If you look at paul's green water when he had an alge out-burst thats how my pond looked. i couldn't let my tank look like that. ) I am now doing 2 water change a wk to try and even it out cos the arowana is a little less hardy to drastic change.

i totally agree with marcus on this. tank and pond definitely have two different
water parameters. and soiled pond is more difficult to handle than a cemented one.
direct sunlight plays very important factor on algae formation, it requires a good
filtering system to keep under check. if you have a good landscape where you can
divert the water and allows it to flow back at the pond, you will have a good chance
of keeping the water clear...but not necessarily clean.