Water changes

[Delphinus]

I did a 100% water change once, solved my nitrate buildup pretty lickedy-split But it was a 20g tank and it had no fish, only a carpet anemone and some corals. But they all liked the outcome ...

There are times when I look at my 110g cube tank now with its elevated nitrates and I wish I could do a 100% changeout, I just don't have enough reservoirs to do it (and I have fish in there so that's no good). But I'd love to be able to change out even 50% or 75% of it just to be a kick-in-the-melon to the nitrates that are there.

Other than the bad salt (Kent, about a year ago? Maybe 2 years ago now, when they had that alk issue??), I've never had an issue from the waterchange itself. But yeah, I do match the temp and SG carefully, and do the premix for 24 hours thing too, so that probably helps a bit. I'd hate to see the results of a large scale water change that introduced a drastic temperature change.

I tell you one thing though, and maybe it's worse for me than others since I have tanks that have at least 5 years of crud buildup in the plumbing, when I turn the pumps off and turn them back on, the stuff that comes flying out of the sump return outputs is something I wonder if it would be better off not having been disturbed and released "en masse" into the water (ie, did I just invalidate my water change). I need a way to scrape out the pipes Or maybe it's better just to redo the plumbing every few years or so

[marie]

It's interesting that nobody is speaking up for the small water changes.

It was comments like this

Well I had done a 50 % water change a few days ago(risky I thought myself )

and this

Really what I would do is (here come the flames) a 80 or 90% water change

that got me curious.

It's not just canreef but on every reef forum I visit, there is a group of people who will tell you to never change out more then 10-20% of the water. I think that a lot of tank crashes could of been saved over the years if people were more willing to trust the lone person who says "Do a 90% water change"

[Aquattro]

Marie, I completely agree. While I regularly do 10 or 15% changes for maintenance, if I thought I had an issue that a 100% change would fix, I'd do it ( well, back when I had a 100g tub for mixing). The "rule" of 10% is just being safe and we always tout "make small changes slowly" in a reef, but properly prepared water is just like the water in the tank without all the crud in it.

[tang daddy]

A 100% W/C is like starting up a new tank and putting a whole bunch of corals in. Hey that's basically what I did well not that fast I waited every other day.

[StirCrazy]

I usaly only did 20% but I moved my tank and/or redid stuff and 5 times I did 100% waterchanges. never lost anything on a 100% change or suffered any ill effects. just match salinity, PH and temp as close as you can, and away you go.

Steve

[marie]

It's hard to get a debate going when everyone agrees with you

Originally Posted by StirCrazy

I usaly only did 20% but I moved my tank and/or redid stuff and 5 times I did 100% waterchanges. never lost anything on a 100% change or suffered any ill effects. just match salinity, PH and temp as close as you can, and away you go.

Steve

It's not very cost effective to do large water changes all the time, only when you have problems . In fact I'm reaching the point where I don't do water changes unless I notice problems starting

[PoonTang]

I think it would depend on what the problem with the old water is. The key is stability. If it just a routine water change where the new water was basically the same as the old water than a 90% WC shouldnt be harmful. If it is an emergency WC than a 50% change could be fatal. Eg. what happens if your tank has a problem and get a pH spike of 9.0 and so you do an emergency WC and thus cause it to drop to 8.2 in a matter of minutes? Wont be a pretty site afterwards. The cure may be more harmful than the disease?
I think you need to know exactly what the condition of the old water is before we make large WC. Would kind of be like adding new corals and fish to our tanks with no acclimation what soever