Water Changes: How much is too much or too little

[Seagars]

I have a 150g tank and was just curious what others think on the level of water changes. How many gallons would be too many (major water changes) or how much is too little (why bother). thanks

[tmz]

I prefer small frequent water changes to provide more constancy in the water chemistry of the tank( major , minor and trace elements). One percent per day is what I've been doing for many years. If more is desired over a short period of time 15% increments per day are reasonable, with some testing for critical parameters IMO.

[ComforablyNumb]

I have a small tank (55g) and I routinely do 60% water changes every couple of months. No deleterious effects noted altho I see the rationale behind doing 1% changes daily.

[blasterman789]

Unless I'm trying to fix something I've always been a believer in conservative water changes. Do them on a regular basis, but if you have one of those tanks that starts to deteriorate rapidly if you aren't changing 25% water on a weekly basis something is wrong, and I'll battle that opinion until I'm bloody.

If you need to do lots of water changes to export nutrients (nitrate) then you need to rethink your bioload and feeding. If you need to do more to suppliment something (alk) or keep water params stable then you obviously need to invest in a couple test kits and a box of baking soda and jar of calcium chloride.

20-25% every two weeks is my highest turnover advice. Any more than that and, IMO, you're trying to fix something that could be achieved via easier means and could/will get out of hand at some point that water changes wont fix, or you just like mixing salt. Local reef store just had all their big SPS tanks get necro'd because they were relying on a generic salt mix and massive changes -vs- training their staff to read test kits. They got a bad batch of salt, and that was that. Had they been doing minimal changes and proper supplimenting the damage would have been far less severe.

[homer1475]

I do 10% every week religiously, but I have a smallish tank and 10G a week is no big deal.

I've kept this husbandry for many years with my FW tanks, so it naturally carried over the the marine side when I started in that.

[bertoni]

Generally, I would keep water changes to no more than 15-20% of the total volume unless there's an emergency. Exposing live rock to air can kill organisms and cause an ammonia spike, although that's rare. Doing many small water changes is a fine idea, especially if it can be automated.

[tmz]

(why bother

High nutrient issues ( nitrate phosphate, organic carbon levels) are rarely remedied by large water changes except for a short time; since, the amount of nutrients in the tank are a result of the balance in inputs( food biological exudates and waste products and decay) vs export via biological and mechanical filtration.
Salt mixes do provide many trace ,minor and major elements ; water changes also draw down excesses to maintain element ratios and levels Direct supplementation for alk and calcium are needed in many tanks even those with large routine water changes.

[Belgian Anthias]

To remove accumulating nutrients water changes are not the solution on the long term.
To add things that are consumed? It will not add enough when not 100% is changed so one must add additives. Expensive additives are added, the next water change will remove partially what was added. Daily or weekly water changes will remove a lot of expensive additives, certainly when top off systems are used.
When changing water? Periodically? For a reason or without a reason? Difficult to answer. Each system is different.

[PedroMurcia]

I make two changes of water (4% -5% each) per week to maintain stable elements.

[bertoni]

Water changes can stabilize the ionic balance of the water if enough are done. 100% changes aren't necessary for our tanks, as far as we can tell, because the ionic balance shifts fairly slowly and exact precision is not required. They also help remove compounds that can cause tinted water, for example.

[tmz]

To be clear:

In addition to some refractory organics removal,

water changes take out some elements and add them(potassium, magnesium, iron, iodide, trace elements etc) back at levels closer to the starting point when the same salt mix is used . Thus they negate the need for many additives and help prevent excess build ups from some elements that may be harmful like copper and other heavy metals as well as help to maintain element ratios like chloride and sulfate. As I noted earlier ,new salt water also adds calcium and alkalinity but in tanks with calcifying orgnaisms dosing those two inexpensive additives is usually required to maintain alk and calcium in preferred ranges. Small water changes won't usually maintain them. Consumption levels for the others are usually handled well with water changes;foods also contribute.

100% changes are not necessary and can be harmful. I know some with nano tanks do rely on large changes for everything including calcium and alkalinity since tiny volume dosing is tedious but great care is taken to match the change water with the tank water in those cases.Even then smaller more frequent chages would be my strong preference.
Smaller more frequent changes promote constancy.
No water changes with a slew of expensive supplements and inadequate testing doesn't cover all of the elements in seawater and provides no means for exporting excesses or maintaining ionic balance.

[malx]

I'm a fan of more frequent smaller water changes. You don't want to shock anything but yes, you want to keep your nutrients in check as well.

[Sawen]

I change one gallon of water every other day on my 25 gallon cube.

[cincyjim]

I change 20% every two weeks. Is that over kill on a 75g tank?

[steallife904]

I do around 7-8% a week on my 140

[bertoni]

20% every two weeks is fine. The tank might do just as well with a 10% change every two weeks, but that's hard to predict. Personally, I'd say just keep with the current schedule if the time and cost are acceptable. If you're a bit more experimental, then switching to 10% probably is safe.

[Mark9]

15% every 2 weeks.

[karimwassef]

I do 25% of DT (15% of total volume) every two weeks (~2% DT per day average).
That's 100gal out of 380gal DT and 660gal total volume every 2 weeks.

[cincyjim]

20% every two weeks is fine. The tank might do just as well with a 10% change every two weeks, but that's hard to predict. Personally, I'd say just keep with the current schedule if the time and cost are acceptable. If you're a bit more experimental, then switching to 10% probably is safe.

Thanks for the feedback! I'll stay with the 20% :)

[Dmorty217]

There are arguments for both (small,frequent vs large, less frequent) I had a chance to speak with Kevin Kohen about this and his 3 office tanks get water changes every week. The pipes for both RO/DI and Reefcrystals are plumbed in the ceiling at the DD facility with float switches in sumps. He creates a syphon at one end and lets the system fill on the 28g for 15 minutes, 120g for 1 hr, and the 180g for 2 hrs. " Performing water changes in this manner is costly, but is the best approach for fish, corals, and inverts to slowly make changes without major disruption to the animals in the display." Clearly he has many more resources available to him at DD than the average person, so it may be harder for you or I to replicate what he does LOL

[jason2459]

I don't do it but my system gets ~1% daily water change 150 times through out the day.

[ostrow]

I don't do it but my system gets ~1% daily water change 150 times through out the day.

Please tell me there is a typo in there somewhere.

[jason2459]

Please tell me there is a typo in there somewhere.

Nope, I use a spectrapure Litermeter III with remote pump. It will dose the amount you want 150 times evenly through out the day.

My setup with failsafes.
http://reefcentral.com/forums/showthread.php?p=23789321&highlight=spectrapure#post23789321

[ostrow]

So you are changing 150% of the water volume on a 180 tank every single day?

You must be spending a veritable fortune on water and salt mix. Whatever works for you I guess!

[jason2459]

So you are changing 150% of the water volume on a 180 tank every single day?

You must be spending a veritable fortune on water and salt mix. Whatever works for you I guess!

1% daily

[ostrow]

Ok. Grammatical error above. Now makes great sense.

[Belgian Anthias]

There are arguments for both (small,frequent vs large, less frequent) I had a chance to speak with Kevin Kohen about this and his 3 office tanks get water changes every week. The pipes for both RO/DI and Reefcrystals are plumbed in the ceiling at the DD facility with float switches in sumps. He creates a syphon at one end and lets the system fill on the 28g for 15 minutes, 120g for 1 hr, and the 180g for 2 hrs. " Performing water changes in this manner is costly, but is the best approach for fish, corals, and inverts to slowly make changes without major disruption to the animals in the display." Clearly he has many more resources available to him at DD than the average person, so it may be harder for you or I to replicate what he does LOL

A very ineffective way for changing water!? New water is added and before it has the change to mix it may be partially syphoned away. When water is added that has not exactly the same temperature as the system water then the added water stays together for a while before it mixes. When a bit warmer it will go to the surface, When a bit colder it will decent. When the column of new added water can reach the syphon it is possible a lot of the newly added water is removed before it can mix. Even when it mixes by heavy water movement the new added water will be removed partially before it can ad anything to the system. This is a common problem when top off water changing systems are used.

[kilasic]

Too much of a water change is really a vague term. Say your CA-ALK-MAG, Salinity, etc of your new water matches your tank, a 50% water change is a massive water change in terms of water volume, but it's not too much for the livestock to handle (just likely unnecessary unless it's an emergency).

If the salt mix doesn't match in terms of foundatiom elements (salinity must always match imo), as is the case in a reef tank where these elements can be significantly altered over time, going above 20% may be too much.

Another thing to keep in mind is there are many elements we can't test for that affect a salt mix, so I'd say as a rule of thumb, 40% every month is a good compromise. Keep in mind, i mean overall 40%, so I do a 10% change every week, which prevents flucuations of foundation elements. I did 20% every 2 weeks, but i switched to my current schedule because my LPS and SPS would retract their polyps for a bit with a larger change.

[Dmorty217]

A very ineffective way for changing water!? New water is added and before it has the change to mix it may be partially syphoned away. When water is added that has not exactly the same temperature as the system water then the added water stays together for a while before it mixes. When a bit warmer it will go to the surface, When a bit colder it will decent. When the column of new added water can reach the syphon it is possible a lot of the newly added water is removed before it can mix. Even when it mixes by heavy water movement the new added water will be removed partially before it can ad anything to the system. This is a common problem when top off water changing systems are used.

Not effective at all but when resources are virtually unlimited then nothing is impossible

[ADVRESOURCE]

I have a 240 g DT and large sump. Total water volume is 260g. I was going to do 20g on the 15th and 50g on the 1st of every month. Around 26% each month.

[bertoni]

Say your CA-ALK-MAG, Salinity, etc of your new water matches your tank, a 50% water change is a massive water change in terms of water volume, but it's not too much for the livestock to handle (just likely unnecessary unless it's an emergency).
Generally, I agree that animals can be fine with very large water changes, as long as the salinity is matched reasonably well, as far as changes to the water column itself. The worry for larger changes is that some animals die on contact with air, and that can cause a tank crash. If the tank gets very large water changes regularly, that risk should be extremely small, but for other systems, some caution generally is a good idea. If the water already is in bad shape, though, with a large amount of ammonia, for example, a large water change can be better than the alternatives.

[robbous]

i have a 500 gallon display with another 150 gallon sump water volume i do a 10% change every 10 days i make sure the saltinity and temp are exactly the same i never have any issues. i ll test water before and about 5-6 hours after a water change of crucial things all,cal.nitrate, phos. to see if there are any changes and there usually never is

[karimwassef]

I separate water changes from the mechanisms of the change?

In my case, I have a separate 100gal aux sump to absorb the massive overflow from my surges.

To make a water change, I separate this aux sump from the main (surges off, of course) with a valve. Then, I remove all the water in the aux sump . I add in fresh water and salt mix with aeration and pump agitation for several hours checking salinity and Alk. Then I slowly open the connecting valve. After a few more hours, the valve is fully open again and the surges can restart.

[tmz]

A liter meter in/out set up will spread the withdrawl and replacement into 150 equal daily increments. I use that for kalk dosing. Some day I'll probably automate water changes that way . For years now I've been getting by by with siphoning 1% and replacing 1% into a high flow area of the sump . I use a bucket. 1% is not going to shock anything or effect temperature noticeably. Takes only a minute or two since I keep mixed slatwater on hand .

[tmz]

There are arguments for both (small,frequent vs large, less frequent) I had a chance to speak with Kevin Kohen about this and his 3 office tanks get water changes every week. The pipes for both RO/DI and Reefcrystals are plumbed in the ceiling at the DD facility with float switches in sumps. He creates a syphon at one end and lets the system fill on the 28g for 15 minutes, 120g for 1 hr, and the 180g for 2 hrs. " Performing water changes in this manner is costly, but is the best approach for fish, corals, and inverts to slowly make changes without major disruption to the animals in the display." Clearly he has many more resources available to him at DD than the average person, so it may be harder for you or I to replicate what he does LOL

I haven't heard a good argument for large water changes vs smaller ones . If the goal is quick nutrient reduction or correcting some sort of toxic condition , a large one is useful in the short term but without resetting the balance between import and export of nutrients ;water changes are ineffective for nutrient control.
I don't know what the DD facility is or who the person you spoke to is. How much water is being changed each time?

[jason2459]

Divers Den from Live Aquaria and Kevin has been the main person in charge there for quite some time.