How much water change is to much

So like it says. I am trying to get a couple things in check nitrates are to high and just lost a few corals. I went on vacation and think the house sitter got over zelous on the feeding. they are at 40ppm I am not impressed. I have never wanted to do such a huge waterchange before is 50 percent to much. I was thinking about 100 gallons on my 220 with 45 gallon sump to much not enough? then a couple 20 percents over the next weeks

 

I have done 50 percent before, If stuff is already dieing why not?

the parameter swing is what you want to avoid, just try to get the params as close to the tank as you can(obviously not the nitrates) before you change it.

 

As long at temp, pH and salinity are correct there is no such thing as too much.

 

Everything is going to be on par. I have 2 100 gallon tanks in the basement as I have the three tanks wil ro water in them at all times and then mix salt when time to change. I cant afford to lose the fish though there are some rare ones in there. I can replace the corals easy enough as there is not a ton in there but im trying to get into the sps as we speak. I just want to get the nitrates down. I will monitor the ph and the temp. I also add a pump also to get air in there when mixing. I can do 100 percent I just want to drop these nitrates fast.

 

Do 2 50% instead, it will get your nitrates to around 10. Most fish can easily handle 20.

 

+1 on all above posts

many people when moving a tank, wont take their existing water ( or more of it than is required to transport the livestock and rockwork etc)

so 50% water changes, as long as the parameters of the new water are as close as possible to the water in the tank , are not an issue IME



Steve

 

As posted a few times above^ as long as parameters are the same you will be in good shape. I did a 50% change after I moved with zero negative effects (as far as i could tell). The best way to go about lowering nitrates via water changes is to do 2x 50% water changes within a week or so.
I've seen a chart that illustrated how doing smaller percent water changes to lower nitrates is pretty ineffective and will take months to get readings below 10 and instructed to do 50% changes instead (sry i cant find the site that has the chart).
GL!

 

+1 on fishchkid

its basics mathmatics really so no issues on not having the chart
if your nitrates are 40 and you change 10% of the water , and providing the new water had 0 nitrates - then the best you can achieve is a new level of 36 ( 40 x 10% = 4)

If you perform a 50% water change then the equation is 40 x 50% = 20) so again providing the water you added was 0 nitrates , your new nitrate reading would be 20

Steve

 

K for all the helpful information. in all the years with this tank ive never had to do such a large water change.

 

Hi, I can't understand everyone supporting a water change and especially at the volume everyone is mentioning! A 50% should only be done in an emergency. 40 ppm Nitrates does not warrant this. Overfeeding, lack of sufficient clean up crew and unmaintained filters and sponges along with many other things are usually the culprits for high Nitrates, which I might add, you do not have.
Do you even know 100% that the nitrates killed your coral? Temp swings are more likely a culprit along with large PH and Alk fluctuations. To disrupt a tank by doing a 60-65% change (that is really where you would be as you didn't factor in the rock and substrate) is ill-advised. In an extreme case of nitrates say going through the roof at 60-80 ppm, then yes 2 larger water changes may be in order. For everyone here to go along with the panic is amazing to me.