Water Changes: Where do you stand on water changes for your reef tank?

[Lasse]

I used to do religious water changes on my prior tanks, but I stopped doing them with my current rebuild, and I've been happy with it so far. Full disclosure: I am only now starting to add SPS to the tank, so only time will tell, but here's my thinking...

While water changes can clearly help, it’s also clear that they aren’t sufficient on their own, but it's possible that other methods can be sufficient without water changes, as long as you have a thorough plan.

There are 2 main reasons stated to do water changes: to get bad things out (pollutants, N and P) and to put good things in (trace elements). Let’s look at the math using the following assumptions:

• Water change (WC) is the only method of adding the good or removing the bad:
• System generates 10 pbb of PO4 each week
• System uses 10 pbb of trace element X each week

End of Week	PO4 pbb Generated	DT PO4 before WC	Removed with WC	Added with New Salt Water	DT PO4 ppb Remaining
0					-
1	10.00	10.00	(1.00)	-	9.00
2	10.00	19.00	(1.90)	-	17.10
3	10.00	27.10	(2.71)	-	24.39
4	10.00	34.39	(3.44)	-	30.95
5	10.00	40.95	(4.10)	-	36.86
6	10.00	46.86	(4.69)	-	42.17
7	10.00	52.17	(5.22)	-	46.95
8	10.00	56.95	(5.70)	-	51.26
9	10.00	61.26	(6.13)	-	55.13
10	10.00	65.13	(6.51)	-	58.62

End of Week	TraceX Pbb Used	DT TraceX before WC	Removed with WC	Added with New Salt Water	DT TraceX pbb Remaining
0					100.00
1	(10.00)	90.00	(9.00)	10.00	91.00
2	(10.00)	81.00	(8.10)	10.00	82.90
3	(10.00)	72.90	(7.29)	10.00	75.61
4	(10.00)	65.61	(6.56)	10.00	69.05
5	(10.00)	59.05	(5.90)	10.00	63.14
6	(10.00)	53.14	(5.31)	10.00	57.83
7	(10.00)	47.83	(4.78)	10.00	53.05
8	(10.00)	43.05	(4.30)	10.00	48.74
9	(10.00)	38.74	(3.87)	10.00	44.87
10	(10.00)	34.87	(3.49)	10.00	41.38

As you can see, water changes alone won’t cut it, so you must use other methods to remove the bad and add the good, even if you do water changes. Sure, a 10% water change is an immediate 10% improvement when other methods are more gradual, so you can see the immediate benefit. And I suspect there is often a correlation between religious water changes and good upkeep generally. If your other methods aren’t thorough, or if you get lazy when you stop water changes, then skipping water changes can be bad.


Here’s what I’ve used to get the bad stuff out in place of water changes:

• Filter roller (or socks or pads) for larger organics and floating debris
• Skimmer for organics
• Algae Turf Scrubber for excess N & P
• ROX carbon for pollutants and any tint in the water
• Bare bottom with high flow for detritus on the bottom
• Blowing off rocks and bottom weekly to direct detritus to filter roller and skimmer
• Periodic treatment with a product like Waste Away to remove any build-up
• ICP to confirm no excess bad staff
• Water change only if directed to do so by ICP (hasn't happened, at least so far)

Here’s what I’ve used to add the good stuff in place of water changes:

• Triton 4-part dosing (includes Alk, Ca, Mg and trace elements)
• Specific manual “fine tune” dosing of only those trace elements identified as deficient by a regular ICP test

Water changes can also introduce opportunities for error (forgetting to plug something in, miscalculating the salt added, spills, etc.).

Other reasons for doing a water change?

• Cost? – For larger tanks, the cost of salt for water changes can be more than the cost of an ICP test. It’s the opposite for smaller tanks. Even so, I would do ICP tests either way to be sure that I have sufficient good stuff and no excess bad stuff.
• Vacuuming sand bed? – I designed around this, but I suppose you could also vacuum directly to your filter roller/socks if you still wanted to avoid water changes. Never tried that.
• Restart? – I suppose there could be some other “restart” benefits…? Maybe the good bacteria gets a jump start when fresh water is added? I doubt it, but maybe?

On balance, a solid no-water-change process seems better to me in theory, and it has held up in my first year of the rebuild without corals. We'll see if I need to modify or even abandon my approach as I move forward with SPS.

As a complement - from my build thread

As many understand - i do not do any WC. In a recent poll at R2R shows that is only around 9 % that only change water when it is needed. There is at least 4 different argues for WC in this thread.

1) The need of adding trace elements that normally will be depleted during a time lap.
2) exporting nutrients
3) exporting "bad compounds"
4) Cleaning of different compartments from detritus and organic matter

Let me first argue around standpoint 1.

Trace elements is for me rather essential because many of them have known and unknown biological importance. My goal as the first choice - try to have near NSW concentration of them and as a second choice - dose daily and in this way create a steady flux of just this element.

Before ICP testing - WC was the only way to guarantee that you did not build up dangerous amount of some trace elements because of dosing them. A blind dosing could be dangerous in the long run. Today - a periodical ICP test give you a snapshot of the concentrations before you build up dangerous concentrations. Even the concentrations of trace elements that in NSW is so low that ICP can´t show them - an ICP test shows if you are over the threshold or not.

With ICP testing - it is possible to dose trace elements (and macro elements too) in a safe way

Does WC with the finest quality of synthetic dry salt mixes guarantee NSW levels of trace elements (and some macros) or even if you have it in your actual WC mix or not?

I will say NO. Why - it is math and physics.

Math

When you mix your salt water - yo normally use between 36 - 40 grams dry salt mix to 1 l of water in order to reach 35 psu. In this exempel I use 40 g/l just for simplify.

NSW concentrations of - for exempel
Manganese -> 2 µg/l (ppB) = 0,002 mg/l (ppm)
Zink -> 4 µg/l (ppb) = 0,004 mg/l (ppm)
Iodine -> 60 µg/l (ppb) = 0,06 mg/l (PPM)
Strontium -> 8 mg/l (ppm)

This means that every 40 g salt mix should contain 0,002 mg Mn, 0,004 mg Zn, 0,06 mg I and 8 mg Sr.

Every kg of salt mix (good for 25 l) should contain 0,05mg Mn, 0,1 mg Zn, 1,5 mg I and 200 mg Sr

This is difficult to obtain but possible to do if you do the mix and use all of it in one batch. For me - I want to change 10 % (30 l) - I should do a mix of 1,2 kg salt that contain 0,06 mg Mn, 0,12 mg Zn, 1,8 mg I and 0,24 g Sr.

This doable if I mix and use all of it in one batch.

However - this is not the way it works. You buy - let us say a 22 kg bucket and use maybe 1,2 kg of this in each WC batch. This 22 kg batch should contain 1,1 mg Mn, 2,2 mg Zn, 33 mg I and 4,4 g Sr. And now - it needs to be evenly mixed because you take out only 1.2 kg of dry salt mix

Further on - before it reach your home - this 22 kg bucket have been done in a factory. if they mix batches of 22 kg - it is ok - but I doubt they do. Let us say that they mix 1 metric ton in every batch (it is a small factory)

Physical

This means that they have to in every 1000 kg dry salt mix put 0,05 g Mn; 0,1 g Zn, 1,8 g I and 200 g Sr. After this it needs to be evenly mixed. This is the elephant in the room - it is impossible to mix these small quantities in 1 metric ton of salt.

And - there is impurities in other salts that´s in use in the mix - the finally trace content is a lottery.

I hope that this math (if it is correct but even if it is 10 fold wrong - it still stands) will definitely kill the argue - I do WC in order to guarantee my levels of trace elements

Sincerely Lasse

Note

In my post above - I talk about synthetic salt mixes. There is other commercial salt mixes based on a solar evaporative processes and boosted with some compounds that disappear during the evaporative process. There could the content and spread of trace compounds and some macros really be the same as NSW. In the start of my aquarium (and if I need a WC today) - I use these types of salts. However - I have noted that sometimes especially heavy metals can be boosted of these salts - or at least the one I use.

Sincerely lasse

Sincerely Lasse

 

[LDog74]

1. 225 gallon display with 40 gallon sump. (Tank has only been up & running for 2 weeks). Just set up my automated daily water change 1% 2.6 gallons per day using Neptune DOS yesterday.

2. With my other 40 gallon tank & previous tanks owned, I have noticed corals and the tank itself seem to perk up after a water change usually 10% every week. So with my new build I knew an automated water change was going to be designed in for less maintenance. It is effortless and good husbandry so why not. (Aside from the cost).

Using RO/DI & Red Sea blue bucket. I also have access to natural sea water which I will also use from time to time. We have been having a Red Tide here in San Diego so I started the tank with RO/DI & Red Sea.

 

[drblakjak55]

Whatever you do, do it regularly Been keeping all kinds of fish for fifty years And monthly 25% water changes after a vigorous rock and sand shake up works. The ocean is constantly refreshing itself and we are trying to recreate a piece of ocean.

 

[SniffanyB]

Pretty simple today. I think it's been a while for a site-wide poll on water changes so let's do it! Let's talk about water changes and where you stand concerning your tank!

1. How often do you "change out your water" in your reef tank, what percent and how many gallons is your system? Or do you even?

2. How important or not important do you think water changes are for your reef tank?


@CMO no water change reef! Thread here.

We have a 32.5 gallon mixed reef tank and do weekly eater changes. IMO small frwuesnt water changes are needed to keep your parameters stable. I have SPS, LPS and soft corals and with the finicky SPS Acros I need a stable water environment for them to be happy and thrive. Which in turn makes the other tank critters and corals happy. I'm new again to the saltwater world. We also have freshwater aquariums that thrive just as well.

 

[Macey’s Reef]

1% daily AWCs. Tanks (5) super consistent & stable. Before starting AWCs I noticed the corals went through a minor reaction on 10% manual WCs. On my anemone tank manual WCs increased medium nems splitting. When I added AWC to my nem tank the nems could get much larger consistent with my goals. No science, just my personal experience.

 

[ocsurferdad]

I have done 10-30% a week, 20 % a month and none for months.

Now I do 1% a day. This seems to be working the best of everything I have tried.

Slow and steady

 

[Whasmack]

Depends on the type of system I am running.
For my small 40g breeder tank that runs Zeovit - water changes per the system instructions.
On my 300g SPS heavy tanks - no water changes. I've done a couple over the years, but they never solve an issue.
Salt is too expensive to do large water changes on big systems that chew through nutrients & elements.

 

[guyhives]

I have done 10-30% a week, 20 % a month and none for months.

Now I do 1% a day. This seems to be working the best of everything I have tried.

How do you do that? Presumably with an automated system? I am keen to do this, can you tell me an affordable way?

 

[vlangel]

I have a 56 gallon display with a 30 gallon fuge and 20 gallon sump. Its heavily stocked and fed. Filtration is mostly biological with live rock, DSB, and macro algae. I do about 10% weekly water change and dose trace elements. Have almost no nuisance algae except film algae on the glass that I deal with once a week.

 

[DeniseAndy]

With my more mature tanks, I do them when I notice the need or every couple weeks. If algae is a concern (like now), I do more to get the algae pulled and sucked out. Before my move to the new 210g, I would go months before water changes. the gorgs loved it.
I have to replenish my 20g more now with clams, but still not too bad. Not too much else fighting for the elements.

 

[brandon p]

Pretty simple today. I think it's been a while for a site-wide poll on water changes so let's do it! Let's talk about water changes and where you stand concerning your tank!

1. How often do you "change out your water" in your reef tank, what percent and how many gallons is your system? Or do you even?

2. How important or not important do you think water changes are for your reef tank?


@CMO no water change reef! Thread here.

This is obviously a very nice tank that took a lot of planning and work. And money. I wonder if anyone out there has a reef tank, that thrives without water changes, but that handles nutrients and trace naturally/biologically? As in sponges, mangroves, flow, etc. If so PLEASE SHARE! Thanks

 

[Lasse]

This is obviously a very nice tank that took a lot of planning and work. And money. I wonder if anyone out there has a reef tank, that thrives without water changes, but that handles nutrients and trace naturally/biologically? As in sponges, mangroves, flow, etc. If so PLEASE SHARE! Thanks

The goal with my tank according nutrients is to manage it mostly internal. But I still have to put in feed from the outside. However - the traces can be more tricky. Of cause I can use river water as top off or maybe mineralize the top off water. Calcium and alkalinity - however - they will be needed to dose as normal but a good calcium reactor maybe can fix that and compensate the pH drop through high pH top of water. So its doable to 95 % at least.

Sincerely Lasse

 

[Beth Villmow]

1) never if it is not an issue
2) Could be important if it is an issue - other times - not important for MY tank

Correct myself - i run Triton Core 7 and have to compensate for elevated salinity with around 0.65 L a day - it means around 0.2 % WC a day


Sincerely Lasse

Your tank is very pristine looking. Amazing!

 

[Rick Mathew]

Continuous ---10% change / week

 

[jrock flimflam]

135g Display + 35ish between sump and new Fug.
I am pretty sure I had a cucumber die inside a rock that caused a nitrate bomb to go off.
Ended up with GHA and Green Turf Algae by the time it was all done.
Due to all this I have been doing a 5g per day, every day, but after I get the Turf gone (GHA is gone) not sure what schedule I should use.

 

[H3rm1tCr@b]

I’m currently holding off till the Dino’s finally go away with my tank. Normally I would do one every couple months or so

 

[Jordan Parker]

When I had first entered the hobby I was all about my weekly 10% water changes, but then I began asking myself "why am I doing this?". After mulling it over through the course of a weekend, I chose to test both my fresh saltwater and my allegedly spent saltwater, only to find that there was really nothing notable wrong with my tank water. I began pushing my water changes by an additional week at a time and found that my corals were, much to my surprise thriving and beginning to show some more vivid colors, some that weren't doing great were beginning to bounce back as well.

I've always used the balling method and ran a light carbon dosing regimen with oversized skimmers and used carbon and GFO reactors, at that, trace elements were always replaced along with the big three.

I am however going to be trying my hand at daily 1% changes in the near future to see if things react well to it, but I honestly think it's not going to make much of a difference in my system.

 

[Michifu5]

Pretty simple today. I think it's been a while for a site-wide poll on water changes so let's do it! Let's talk about water changes and where you stand concerning your tank!

1. How often do you "change out your water" in your reef tank, what percent and how many gallons is your system? Or do you even?

2. How important or not important do you think water changes are for your reef tank?


@CMO no water change reef! Thread here.

I do a fortnightly water change in my 30G (20%)
Running an algae reactor (Pacific Sun) and nearly 0 phos and nitrate - now my battle is to keep nutrients up (perhaps more fish , food or dosing nutrient)

 

[jasontaylor]

Reefing is both an art and a game. You get points by how good things look and how much exciting activity you have in your reef system. But, each time you do a water change, you loose points. The winner has constructed the perfect ecosystem that needs only light radiation to power all that it does, and is ready to go into orbit on a spacecraft where water changes are not as cheap. Once we have perfected recycling in an aquarium, only then are we ready for O-Neil-class spacecraft.

 

[vlangel]

I do weekly WCs. Having been an aquarium tech for a LFS and seeing aquariums run for decades without major problems or crashes has convinced me that WCs has its merits!