Water change too much?

[jsavage6]

I just got back from vacation and my tank, understandably, is looking very dirty. I want to to a 30%-40% water change, would that be dangerous to the fish/coral?

 

[Dbichler]

No you can do as big as you want just match all parameters

 

[Mr. Mojo Rising]

Even a 90% water change will do no harm to fish or corals or inverts (just match the water temp and salinity). I very frequently do large water changes, sometime 50% and more, no harm done.

 

[mnl119]

I just got back from vacation and my tank, understandably, is looking very dirty. I want to to a 30%-40% water change, would that be dangerous to the fish/coral?

The answer is that it could be. I've killed off the bacterial cycle in the past by changing too much water and being sloppy doing so. You will probably be OK if you closely match salinity and temperature, and adding the new water slowly.

 

[brandon429]

There are no cycle kills. What happened MN is you kicked up waste during the pour back


the water change itself is never harmful. depending on your sandbed, it sure can be indirectly. If your tank is dirty you need to rip clean it. I watch folks avoid rip cleans when the tanks go eutrophic because they claim it's too harsh of a move, just had one this week decline it in a blackened sandbed reef on the verge

all I have to do is sub to comments and await the fish loss/crash update in a few mos, he'll rock slide it or pour in too fast. or buy a goby to push up sand that hasn't been pushed up in years and is solid black in the cross section

I will then link that example to our old tank syndrome complete wipeout/I tried to help 6 mos ago threads heh

in those threads we contrast not listening to the awesome effects of listening to recommends for tank rehab moves.
B

if you don't rip clean it, then you have a 99.5% chance of nothing going wrong with a big wc. the other .5% is MN and a few total wipeouts, a few fish only wipeouts, and a bunch of cyano outbreaks that's for sure.

 

[Dbichler]

I’ve done hundreds of large water changes never had bacteria issues with rocks being out of water for hours

 

[brandon429]

for sure. agreed. what organic waste upwelling causes always gets blamed on cycling bacteria. everything a test kit says as nh4 is blamed on dead cycling bacteria/always.

 

[Tired]

The answer is that it could be. I've killed off the bacterial cycle in the past by changing too much water and being sloppy doing so. You will probably be OK if you closely match salinity and temperature, and adding the new water slowly.

Your water column holds some bacteria, but the vast majority of it lives in your live rock. Unless you also change out the live rock when you do a water change, or leave the rock out of the water until it dries up, you won't hurt the cycle. There are people who do 90-100% water changes on heavily fed pico reefs, with no problems whatsoever.

 

[brandon429]

want to add one thing in support of Mn's finding

I have for sure seen api and red sea ammonia test kits spike up bigtime after water changes, or during rock moves, adding stuff from a lfs.. what these test kits do is lunacy sometimes, so anyone seeing that will legit doubt bacteria.


7/8th's of our false cycle stall study threads are exactly that. no seneye owner goes through this; they spent $200 to opt out of cycle fearing.

 

[NMU1963]

I just got back from vacation and my tank, understandably, is looking very dirty. I want to to a 30%-40% water change, would that be dangerous to the fish/coral?

I’ve been running a180 for 6 years. Add another 30 gallons in the sump. Mixed coral/fish. I do a 25% WC every 2-3 weeks. I have done larger changes and as others have said as long as you keep salinity and temp similar you should be fine. Your corals will thank you

I just got back from vacation and my tank, understandably, is looking very dirty. I want to to a 30%-40% water change, would that be dangerous to the fish/coral?