Why 10% & Can You Change Too Much Water?

[Forsaken77]

Like the title says, is it possible to cause any harm by changing too much water, during a water change, in one shot?

Where does the 10% weekly water change number come from? Why is this the recommended amount?

Doesn't apply to uncycled tanks, QT tanks, ect... Mature tanks only.

 

[Crabs McJones]

Not sure why alot of people settle on 10%...probably because it's usually a nice round number and easy to figure out. With that said alot of people will do 20%. And you can do some harm by changing to much water. If you were to do anything over 50% you're changing out to much water and it can shock the system and potentially cause a mini cycle.

 

[Robink]

It would also affect your parameters if the new water does not match your tank's water.

 

[Forsaken77]

Isn't the salt mix you use supposed to have the correct parameters?

How can you potentially start another cycle? Isn't the bacteria still in the tank (substrate, media, sump)?

 

[Reefltx]

Isn't the salt mix you use supposed to have the correct parameters?

How can you potentially start another cycle? Isn't the bacteria still in the tank (substrate, media, sump)?

Supposedly, but if you’ve been in the hobby long enough, none every do. Bacteria’s everywhere, but it’s not just that you’re stripping away.

 

[Picesduh]

If you change 100% your fish and other livestock would be out of water and may die [emoji23]

 

[mitch91175]

Like others have mentioned, the 10% is more to not drastically change your overall water parameters, mainly ALK. The others aren’t as critical (at least to me) but having major ALK swings can cause issues.

With that said, if you keep you parameters close to the level of your salt mix and you are testing the fresh mix to ensure that they are similar, you can change whatever percentage works for you situation. Just know that when you change water, any beneficial bacteria that is in the water column during the change will also he removed as well. Most will still remain attached to your live rock, in sandbed, etc but you will be removing a percentage when doing you water change.

Also sometimes salt mixes can have a little ammonia in them as well once mixed so you want to try not to change too much if that is the case. Nothing that is critical and should cause issues, but still can be present.

 

[that Reef Guy]

It All Depends on the Salt that you use and Your Parameters.

I do 70 Percent Water Changes.

I have seen People do 100 Percent Water Changes.

 

[lbacha]

The more water you change at one time the higher the chance of large swings in key parameters salinity, ph, temp, cal, Alk, as well as nutrients (some of us struggle to keep our nutrients up). While you can spend effort making sure you new salt water it perfect it is easier to do smaller changes that won't effect things as much. I do about 15% a week since I have a nano but it is automated with 2 BRS dosers to change out 2% a day. I mix up salt make sure the salinity is correct and that is all I worry about since it is such a small amount each day thinks like temp, ph, Alk and cal don't really matter

 

[Elegance Coral]

You can change as much water as you want. It will not cause a cycle. The bacteria that do the work and prevent cycles are living in the rock and other structures in the tank. There isn't enough in the open water to cause a problem. Even if you change 100% of the water. I just got through doing a 95% water change on a 1200 gallon. The results, everyone looks much better the next day.
Disturbing a filthy sand bed or other such areas, during the water change can cause cycles though.
Water changes are your best friend. Don't be afraid of change water. The cure for most problems in his hobby is water changes. That's probably why the industry tries to caution against large water changes. They couldn't sell all those snake oils if people just changed water when they had a problem.
The larger the change, the more likely parameters will change. When dealing with delicate creatures, like SPS, the larger the water change, the more attention you need to pay to equalizing parameters.
Peace
EC

 

[Elegance Coral]

Isn't the salt mix you use supposed to have the correct parameters?

Yes. Typically, if you're using the same salt, and mix it to the same salinity, the parameters should be very close. Unless you have a bunch of stonies that are pulling calcium and carbonates out of the water. In that case, you should be keeping up with it anyway.

How can you potentially start another cycle? Isn't the bacteria still in the tank (substrate, media, sump)?

Yes they are. Simply replacing the water will not cause a cycle. Disturbing a filthy sand bed in the process, which increases the rate of decomposition, and can potentially release harmful substances all at once, can cause a cycle and/or other major issues.

Peace
EC

 

[DancingShark]

I have seen nano tank owners weekly change all of their tank water. I though that was a common thing to do.

 

[WV Reefer]

I like to do 30%....... it’s a personal preference.

Nano tank keepers are known for changing out a lot of water volume and pico tanks will often do 100%. It depends on what you need to accomplish.

 

[ca1ore]

Isn't the salt mix you use supposed to have the correct parameters?

How can you potentially start another cycle? Isn't the bacteria still in the tank (substrate, media, sump)?

As soon as NSW is added to your tank the parameters begun to change - some things added others depleted. So while NSW may always be the same before added to your tank, it's not going to be the same as the water it replaces. If we accept that stability is important, then common sense suggest that frequent, modest water changes are better than infrequent large ones. Nothing magic about 10% ...... I prefer to do 11.5789% water changes.

Anyone who thinks just changing water can start a cycle misunderstands how a biofilter functions. Now, if a water change involves vigorous stirring of the sand bed, that could cause issues; but the simple process of swapping a volume of old water for new will not trigger a cycle.

 

[DSC reef]

When I moved our tank I did a 100% water change and it caused a bacterial bloom for a few days. No sand bed and all the same rock. I hope I "fundamentally" know my tank. Lol.

 

[DSC reef]

I've always done 15-20% water changes. The new water never matched perfectly to the tank water due to uptake from the coral. Still not enough of a swing to cause issues though.

 

[jda]

I mix water in convenient containers for mixing new salt. For me, this is 44G on a 240g tank, so I can do 18% or 36% if I double up. That same 44g is a a lot of my 90 gallon frag tank.

The reason is simple... no salt has perfect parameters so I had to experiment with how much to doctor the fresh mix. Full 50g bag of IO, a bit of Muratic Acid and a few tbsp of dowflake and then my water is perfect.

 

[Crabs McJones]

As soon as NSW is added to your tank the parameters begun to change - some things added others depleted. So while NSW may always be the same before added to your tank, it's not going to be the same as the water it replaces. If we accept that stability is important, then common sense suggest that frequent, modest water changes are better than infrequent large ones. Nothing magic about 10% ...... I prefer to do 11.5789% water changes.

Anyone who thinks changing water can start a cycle fundamentally fails to understand how a tank functions. Now, if a water change involves vigorous stirring of the sand bed, that could cause issues; but the simple process of swapping a volume of old water for new will not trigger a cycle.

I stated it could start a mini cycle....COULD not that it would. Changing out a large volume of water has proven in the past to cause bacterial blooms.

 

[ADAM]

20-30% every two weeks for me. From my experience a lot of the people will start changing more when nutrients are an issue; low flow/ over feeding/ high nitrates/ high phosphate... algae and cyano problems. I have a 92 corner tank and once I figured out the right flow directions and amount (not blowing sand outta the corners but enough to keep detritus suspended) I found my nutrients were much easier to keep in check without weekly WC. The "right salt" makes a lot of difference as well with regard to problems arising from larger WC, my system does much better with Aquaforest Reef Salt as far as additions to doctor the water to match. AFRS most closely mixes were tank seems to gravitate to naturally without much additions of extra additives. Its probably best to find a system (amount) that works for you; 15 gal- 6 lbs salt- 2 tbsp buffer- 15 ml Ca.

However 10 is a magic number for some reason... Dont believe me ask the late comedian George Carlin, he did a great bit on the number 10 in society. Probably find it on Youtube/ web somewhere pretty easy.

 

[Forsaken77]

Was curious, because I usually change 20 gallons on my 93 cube bi-weekly. Sometimes I do 40 gallons if life gets in the way.

The sand bed thing is curious though. Because I have vacuumed 100% of my sand, when it was dirty, use a 50 micron sock all the time, and would just change the sock the next day after everything still floating was gone.

Is that why you're only "supposed" to do some of the sand bed at a time, so you don't cause issues? But then it always seems like by the time you finish the last 25%, the first 25% is dirty again if you do it quarterly, lol.