Please visit our Sponsors
FAQs About Water Changes for Marine Systems: Frequency & Amount

Related Articles: Marine Water Change, The 'Perfect' Water Change Regimen? by Scott Fellman, Water Changes, Exchanges by Anthony Calfo, Captive Seawater Quality, General  Marine Maintenance

Related FAQs: Water Changes for Marine Systems 1, Water Changes for Marine Systems 2, Water Changes 3, Water Changes 4, & FAQs on Water Changes: Rationale, Gear/Tools, TechniquesAutomation, Trouble/shooting, & Water Top-Off Systems, Evaporation/Water Make-Up, Treating Tapwater Marine Water QualityMarine Plumbing

As a general rule, some ten-twenty percent a month minimum. Best more frequently, smaller percentages. Absolute best, continuously as in "drip" (e.g. the folks at Monaco). Never have seen a system that the simplest, cheapest, most-assured method of improving, maintaining water "quality" (as in overall viability) wasn't frequent partial water changes. Folks who profess otherwise are trying to sell you something. Check out which is cheaper per desired results... and keep using pre-mixed synthetic or stored-treated natural) for changes.

Re: SW fish mortality... more GIGO, generalizations in, g out. Now water chg. %   7/27/17
Thanks bob. Always wished there were more hard science when it came to this, more in the direction of cat and dog understanding.
<Google the names Andrew Rhyne and Kathleen Wood. These two have been gathering such data>
I will throw one more in there, misinformation, taking ideas from others and thinking they will work for you.
Was just told by someone at a reputable online fish e-ticket that more than a 25 percent water change at a time is harmful and removed beneficial bacteria. I always thought and still believe organic build up in a fish only set up is bad, and the good bacteria existed on rock, sand tank, and very little in the water.
<Mmm; am leery of generalizations... Would require information on how the replacement water was made, how the old water was removed...>
Never heard of too big of a water change in a fish only set up, as long as temp, salinity and other spec param.s are close.
Thanks again Bob.

Sm./Nano water change frequency    9/18/13
Hello WWMCrew,
I have a nano 'aquarium' (10 litres UK), and I was wondering how often I should perform water changes. I was initially performing one 15 - 25% change per day, but I've read that once a week should suffice?
<I would likely default to the weekly changes... but as a general rule, the smaller the volume, the more frequently I would perform... AND most important to mention; I'd ALWAYS have pre-made water on hand with such small volumes for "emergency" change-outs>
I have one red cherry shrimp (will be adding a few more quite soon).
Parameters are 0 ammonia, 0 nitrite and around 2 nitrate. The ph is 7.6 - 7.8.
<Mmm, I'd bolster the pH (in the change water)... likely to 8.2; with a commercial product... SeaChem's lines are faves here. Reliable, miscible>
Thank you.
Kind Regards,
<And you, Bob Fenner>

Water Changes and Overfeeding   4/2/12
I read the article located here
http://www.wetwebmedia.com/scottsh2ochgart.htm and so I thought to myself... if two is good, then three is better!  So, I started doing 1 gallon water changes on Monday, Wednesday, and Friday.  Then my tank's levels went crazy - ph 7.8, ammonia .25, nitrites have always stayed at 0, nitrates possibly 40 (it's kind of hard to read that one, API saltwater master kit).  So I had the fish store test my water and they said I was probably over feeding.  I was doing two different flake food products, once in the morning and once in the afternoon.  I have 1 yellow tail damsel, 2 peppermint shrimp, 5 hermit crabs (red and blue legged), a Nassarius snail and other algae eating snails.  I also have 2 candy cane corals, four or five groups of Faviid corals I got on live rock and some soft corals including some Zoas and star polyps.  To feed the corals I used dried krill or frozen shrimp three times a week and would put some phytoplankton in about once a week.  So the fish store suggested that I not do any water changes until the levels were better, which they are now (8.2, 0, 0, 20ish).  And he also said that I should not change the water so frequently.
I also plan on feeding the flake food once every other day and krill once a week.  Should I use the phytoplankton at all, should I get zooplankton?
I feel like I have to relearn everything about every couple of weeks!
Thanks for any input you provide.
>Afternoon Paul. You do not indicate the size of your tank so it is difficult to determine whether or not the water change process you are mentioning is helpful or harmful.  In addition, this information will also help determine whether you are feeding too much.  That being said, on the surface I would say that you are indeed feeding the fish, coral, and tank in general to heavily.  Please let me know what size tank>
Re: Water Changes and Overfeeding, NO3    4/3/12

Thank you for the reply.
<You are welcome>
As soon as I hit the send button I realized I didn't say what size tank I have!  Anyway, it's 28 gallons.
<Based on this size, yes, you are overfeeding>
There's a 3 inch DSB, so 3 gallons a week is more than 10%.  The fish store guy said that the less you do to the tank the better (i.e. change the water once a week, maybe twice, but definitely not 3 times).
<10% a week will be plenty to help replenish trace elements as well as export nutrients.  Although in theory more are not harmful, in that small a volume of water, changing water that frequently may contribute to frequent swings in water chemistry if the water is not perfectly the same.>
But then again it seems there are as many ways to do things as there are people in the hobby!
Thanks again, Paul
<You are welcome, Bobby>

Weekly Water Changes 3/29/12
Hi WWM Crew,
<Hello Alan>
Currently I'm keeping a reef tank with LPS, SPS & soft corals. One of my weekly regime maintenance is doing a 10-20% water change using distilled water with Red Sea Coral Pro salt. Will this be sufficient as I do not wished to do a daily dosage of calcium, magnesium, ph/dKH buffer and so on.
<All depends on the amount of SPS/LPS corals that are in the system. 
Weekly testing of those parameters will determine that.>
Thanks in advance.
<You're welcome.  James (Salty Dog)>

Water Change frequency and amount 2/8/2011
Dear Crew,
I have a 40 (UK) gallon tank with the equipment listed below.
24 Pounds of Live Rock,
20 Pounds Coral Reef Live Sand,
Wave Maker 6000L/H Powerhead,
Wave Maker 3000L/H Powerhead,
Deltec MCE 300 Hang on Skimmer
Aqua One hang on Filter (with floss & carbon to polish water)
Corals include, large toadstool, mushrooms, brain coral, polyps and a few others.
Fish are Green Chromis, Yellowtail blue Damsel, Maroon Clown & Small Picasso Trigger.
Corals and fish all doing well.
<No troubles with the Trigger in that mix yet? That is too small of a tank for triggers. Read here: http://www.wetwebmedia.com/pictrigfaq2.htm >
Tank looks really healthy.
The tank has been running for 14 months.
Now my main question is, I do a 10 gallon water change every 4 weeks. What I want to know is, would there be any benefit of doing a 5 gallon water change every 2 weeks instead.
Does it make any difference. I am happy to do it either way.
<Well, it sounds like you are having success with your approach so far.
However that is more than 25% at once. A very good article is here...
http://www.wetwebmedia.com/scottsh2ochgart.htm  Scott endorses small more frequent changes.
There are links to several FAQ's pages from there that provide other opinions. I lean toward relatively larger less frequent ones because I am lazy. I feel that if 5% versus 10% makes a noticeable difference in your water chemistry, you system is not stable. But 25% monthly seems a bit drastic to me. I would go to 5 gallons every 2 weeks. One benefit is that 5 gallons is much easier to manage than 10. I can mix 5 gallons in a bucket under my stand, but for 10 or more, I have to break out the Rubbermaid garbage can and then my husband gets annoyed with all the aquarium stuff laying around.>
Also I have red bubble algae on the back glass about a quarter of gals full. It has been there a while not got any better or any worse. What is the best way to combat this or will it just disappear.
<See below and read... http://www.wetwebmedia.com/redalgcompfaqs.htm >
Parameters are as of 06.02.2011.
Ammonia 0.0
Nitrite 0.0
Nitrate 20
<This should be lower. With the large changes you are doing, this should be lower. You don't say how many chromis/damsels you have or the size of the two larger fishes. But if more than a couple, and if the "small" trigger is bigger than 1", then the tank is overcrowded and you will continue to have high nitrate. I like a Jaubert style plenum for nitrate reduction. >
P.H. 8.2
<This should be higher.><<Mmm, is fine. RMF>>
Phosphate 0.25
<This is contributing to algae.>
S.G. 1.022
<This should be higher. Oceans are 1.024-1.025. Fish stores keep their S.G. low like this to help keep Ich at bay and to slightly reduce salt usage (they go through a LOT of salt).>
Thanks in advance
Gary (Leeds UK)
<Welcome! Alex>

extreme water changes, SW   7/1/10
Why do we not do extreme water changes. Like tide-out and tide-in?
wouldn't it be beneficial to empty the display (80%) and refill it with fresh SW.
<Too much change too soon is to be avoided... and it's not practical, really possible to test the "new" vs. old water to determine how different they are. And the expense... Bob Fenner>

Water changes in a troubled reef tank, 3/1/10
Dear Crew,
Thank you for running such a great website and resource for we novice types! This is my first time writing all, so please excuse the rambling.
<No problem.>
I have been searching the FAQs and I am more educated now than ever but I still have a lingering question on water changes. But first, a little background on my tank:
100 Gallon reef, 30 gallons in the sump
ASM G3 Protein skimmer
Magnum 350 for Carbon
4x96 power compact lighting
100 lbs of live rock
Soft corals and fish only. I know my lighting won't support stonies (I would love to though)
2-2.5 inch sandbed
In operation for 3 years, same configuration, bur livestock has changed slightly
1 Hippo Tang, 1 Zebra Tang, 1 Royal Gramma, Mated Pair of Clowns, 3 Fire Shrimp, few red hermits, and a Diamond Goby (the newest addition)
My tank has had a rough run due to many factors. My RO filter is located outside, and we have had horrendous cold weather. Then the RO gave up altogether. Then I stopped doing regular water changes. This is my fault, and now I am cleaning up the mess.
<Not fun.>
I just replaced and upgraded the RO/DI system and changed its' location so that outside temp won't be a factor.
What I am worried about is when I was doing regular changes, it was 1 large change a month (20-25 gallons) rather than several small changes. I have now put myself on a tight regimen of two 5 gallon changes a week (Sun and Wed) and in the past 2 weeks have changed 50-55 gallons in two large changes (once for removal of a ChemiClean application, once to do a full cleaning of the sump). Do I need to worry about taking too much water?
<No, not really. I would avoid doing more the 50% at a time, but otherwise you should be fine.>
Can I do 15 gallons a week?
<Sounds like a good amount to me.>
My tank turned into a hair algae paradise and I want to correct that in the worst way. I don't want to kill the tank in a fit of water changes though. Am I worried about nothing?
<Mostly, there is some risk with large water changes, or even relatively small ones with vastly different water parameters, but I think you should only see improvement from 15-20% water changes a week.>
Thanks in advance!
Phil Aenchbacher

Very Simple, But Necessary Information...7/16/09
Dear WW Media Crew,
You guys are awesome and the site is such a wealth of information!
<Thank you.>
I read the link on your site for frequent partial water changes. It said a 5%-10% weekly water change is recommended for larger systems, and up to twice that amount for smaller systems. I have an 85 gallon reef tank, so what would be your recommendation in gallons per weekly water change? Not sure if I am considered "large" or "small", or more than likely, "in between".
<Around 8-10 gallons every other week should be fine.>
Also, I use Tropic Marin Pro Reef salt mix, which I feel is a high quality product.
<It is and is my fave.>
My goal in the frequent partial water changes (among keeping pristine water parameters for all the inhabitants in the tank) is to avoid the need to "supplement" the system with vitamins and trace elements, both minor and major. I would rather stay away from additives I cannot measure in the tank.
Weekly, I measure Calcium, Alkalinity, Magnesium, Phosphates, and Nitrates. All seems well. I add 3 drops of Lugol's solution weekly to the sump and usually 2-3 scoops of Tropic Marin powdered Magnesium. My water parameters are all well within the desired range for seawater. If this type of maintenance is followed, what more would you consider to be essential to add to the tank on an ongoing basis for growth, health, and color of corals, fish, and invertebrates?
<None, other than partial water changes to replace minor/major trace elements and dilute nitrate/phosphate levels. Do read here.
I have been guilty of doing too much supplementing at times and gotten into trouble, as the industry has such conflicting information on this subject and the amount of products for the hobby are endless. Is less more?
<Laura, I follow your maintenance schedule almost to the letter, you are on the right road.>
By the way - I do target feed all my corals 3 times per week with phytoplankton and Cyclopeeze. Fish eat well, too.
<You're welcome. James (Salty Dog)>

Water Changes'¦How Often?  5/10/09
Hey Bob and Friends,
On Call (Madeline) here. <From the local HHH groups? Dogfish/RMF here...>
<<Friend Eric here'¦>>
I really love this site.
<<Me too!>>
It is jammed packed with info.
I am new to salt water aquarium care.
<<Ah well, I am not (30+ years)'¦but I do find myself still discovering/learning about and hopefully growing with the hobby>>
I have a fresh water tank and an outdoor pond that do extremely well. The main reason I think, is because I believe in higher filtering than what the water capacity is.
<<Is helpful, yes>>
For example, my 20 gallon tank has two 20 gallon filters. My fish love it and are super happy.
My 80 gallon pond has filters for 120 gallons combined. My new addition, a 60 gallon saltwater tank has a sump and skimmer for an 80-100 gallon tank.
<<Very good>>
My question is this: How often should I be doing water changes?
<<Lots of opinions re'¦but many will agree on 10% - 20% bi-weekly for a start'¦maybe a bit more/more often if needs (water quality/bio-load, other husbandry practices, etc.) dictate. Have a look here: http://www.wetwebmedia.com/water.htm >>
Presently I have only been toping off weekly about 1.5 gallons of fresh reverse osmosis water.
<<Do think about buffering this top-off water (can be done with simple baking soda) to reduce the burden placed on the system by using 'straight' RO water. Have a look here and among the many associated links at the top of the page: http://www.wetwebmedia.com/rofaqs.htm >>
I set the tank up the first week in February. I check my water weekly and my water quality is excellent.
<<Maybe so'¦but the partial water changes also remove and replenish many elements we don't/can't test for. I believe you would be hard-pressed to find any author who 'would not' advocate frequent partial water changes>>
I have 8 soft corals and 8 fish and a shrimp at present, oh and a bunch of hermit crabs and 2 green crabs.
<<You likely have no need for any other 'supplementations' outside that provided by frequent partial water changes>>
Thanks much for any advice you can give me. I have read the articles on your site, but didn't see any with my set up for a new tank.
Thanks again!
<<Happy to share'¦ Eric Russell>>

Large water change frequency 11/17/08 For years I have been mixing my salt with tap water, with mostly unsuccessful results as you would imagine. Too many fish die too soon. Basic water chemistry has always been good (pH 8.2, ammonia + nitrite zero, nitrate around 10), but I have had issues with diatoms and other undesirable stuff in addition to fish loss. I assume the problems all stem from the tap water, so I finally got an RO/DI unit. <Great idea!> I am in the process of replacing most of the "bad" water in the tank with new pure water. I have a 125 FOWLR plus 15 gals in the sump, 130 lbs rock, AquaC EV120 skimmer, good circulation and lighting. Since cranking up the RO unit, I have been changing 25 gals at a time. I have done this twice, 3 days apart, and I'm ready to do another. How often should I do these roughly 20% water changes? How many should I do before adding more fish? I want to get rid of all the TDS, nitrates, phosphates, and other stuff before restocking. <According to the water change calculator on Reef Central, it would take 16 20% water changes to completely get out all the tap water from your tank. To save yourself some time and headache, I suggest just doing a 50% water change and calling it a day. Just make sure the water that you are changing is the same temperature, salinity, and pH. It should be safe to add livestock shortly thereafter. Just make sure to keep up with 10-20 percent water changes every week or two for a healthy maintenance schedule. Also if you should find that your algae problems persist after all this, do some research on your salt mix. It is also very important. Regards, Jessy>

Water changes how much is too much... Reef maint...   8/5/08 Hi Guys, <Bryan> Thanks again for all of your wonderful information! <Welcome> I have a 400g total tank including sump. I had been doing weekly 50g water changes for some time, however I have begun to notice some nuisance algae starting to grow in the main tank sand. I do have macro algae starting to grow in sump. I decided to step up my water changes to 100gallons <Mmmm, I know I should have gone long on those synthetic saltwater manufacturing companies.> and I have been doing this sometimes twice a week to help export some nutrients. <Not the route I would go> How much can I do before I start exporting bacteria, phyto, and other beneficial things? <Some is done with any water change... too much? You're likely past this point> The system is moderately loaded and includes many SPS, LPS, fish, and soft corals. Skimmer is functioning, I am also working on ozone addition but waiting on a few parts for this. <Ah, good... will assuredly help> A couple of points on my water changes: 1.) The system is designed to empty water as water flows in, so the water change is diluted by addition of the water. <Mmm, oh I see below> I don't think this is quite as effective as draining and then filling, but given the system design it's the only easy way to accomplish water changes frequently. 2.) I don't vacuum substrate. The substrate is a very fine sand, I prefer clean up crews to do this job. Is this something that is absolutely necessary? <Not likely so... might be a good idea to stir part of it (with a chemically inert dowel... plastic, wood... every change...)> Most of my snails seems to prefer rock and sides of tank and not the sand. Any suggestions for clean up crews to help keep my sand looking clear? <Mmm, need to chat a bit more before discussing this/these... As in, what's in the sump? Do you have a purposeful, large enough DSB? Culture macroalgae, on a RDP basis? Have you read re? Maybe start here: http://wetwebmedia.com/marsetupindex2.htm The tray on Sumps/Refugiums... Bob Fenner> Best Bryan

re: water changes how much is too much  8/5/08 would you cut back to 50g per week or 100? <I would...> I have to get my ORP meter checked before I start ozone. <I'd set on low mg/h per your volume, metabolism "draw"... not likely to "peg out"... about 300 or so micro Siemens per cm... See WWM re... RMF>

Water Changes, SW  4/9/08 I have a new 150 gallon marine tank. <Congratulations!> It is 2 weeks old and I am currently cycling. When the tank matures (I am not doing a full reef tank, but will have appropriate live rock and limited coral) on this mostly fish tank, is doing a 15 gallon water change each week enough to do a good job? <With adequate filtration and proper feeding/stocking, yes.> I just do not think I could consistently do it twice a week. I have a skimmer and a sump underneath with overflows and two circulating pumps. Thanks, Michael <A ten percent change per week is what you have, usually the recommended minimum. This will be fine with a well planned/maintained system. Just keep an eye on your water quality and increase the frequency or amount of your water changes if needed. Welcome, Scott V.>

Water Changes, amounts/freq.  2/18/08 All, I have read over you FAQ's and still have a question. I currently have a 125g FOWLR with (3) green chromis, mated pair of false perc clowns, 2" diamond goby, and 2" dogface puffer. Currently, I am doing a 5g water change every other day. My water change goes as follows: Put in salt Add RO/DI water and buffer Aerate 48 hrs Test water Change water Is this ok? <Yes.> I was told by a friend, instead of doing the 5g change every other day, to do 20g once a week. Which would be better? <The latter method may be easier on you, mixing and changing all at once. Either will work just fine.> My fish are happy the way it is now, and all levels stay perfect. Obviously, I think everything is good, but I am concerned that the tiny changes may not be as effective as a larger change over the long run. <They are very much effective, in some ways better. By making many smaller water changes you avoid any rapid fluctuations in system chemistry/temperature.> Thanks for your info, Skaife <Welcome, Scott V.>

Re: Calcium / Alk Question, and water change periodicity/amounts  2/10/08 .....Thanks! As for water changes I have a bucket of pre-mixed salt water. Once a day a drain opens up from the sump, we then add 7 gallons of fresh pre-mixed aerated salt water to the tank, the remainder drains out of the system. This achieves 50 gallons per week. Based on this description, it is still ineffective? My understanding is that more frequent small water changes are better, by going daily I am taking this to the extreme. <David Burochowitz, editor of TFH magazine did a study on water changes and the mathematical reduction of nutrients when water changes are done in smaller frequent schedules or in much larger frequent schedules. His study proved not only mathematically, but also in his aquariums kept that larger water changes are much more effective than smaller ones. The study was done with control tanks to verify results. In summary, I advocate larger weekly water changes than smaller daily ones. You are basically doing a 1.75% daily water change. In my experience and understanding of dilution of nutrients the larger water change would be more effective.> As for the snowstorm, how high of a pH would spark this, 8.4? <The pH would need to be closer to 9 or higher. For now double check your test results by using a second test kit and do a larger water change. (around 50 gallons) This should help a lot. I would like to know what the Alkalinity level is after 2 large water changes. It should fall back to a reading of 8-10 DKH.-Rich> Best Bryan

Twice Weekly Water Changes...! Dear Scott F. <Hi there!> If your the ear today, I have NO questions.  This is a pat on the back.  Your 5% water change article is pure genius.  In one week, ONE WEEK... I noticed water becoming crystal clear, corals "perking" and one happy blue Pacific tang. <Cool!> My 100G reef is reborn and the water change is a snap.  Thank you, Thank you, Thank you. <You're VERY welcome! It's great to hear that this technique is working for you! It only sounds tough, but it really does work! I'll bet that our fellow hobbyists would have a lot fewer algae problems, elevated nitrate levels, and enjoy just better overall conditions for their animals. Keep spreading the word on this technique! It's funny, all of my skeptical friends who embraced this technique have been thrilled with the results, too. Could it be that water changes are a good thing? YEP!> By the way. read the Deep Sand Bed article and tried it with 4 inches of aragonite... SWEET!!  All of you deserve recognition. Sincerely, Steve Collyer Modesto, California <Thanks so much for the kind words, Steve! We have some very special people on this Crew who really love sharing with our fellow hobbyists! Be sure to keep sharing your experiences with others, so that we can all benefit and learn together! Regards, Scott F>

A Little Change Is Good- What About A Lot? (Big Water Changes) Dear on-staff WWM water change guru: <Scott F. on call tonight> I've become somewhat suspicious at the rainbow of expensive marine supplements available, and the claims each make about not only the benefits of using their product over others', but the necessity of using them, period. <Well worth questioning> Running some numbers, I've found that it would be much cheaper to up the water % I change every week from about 15% to 25% and quit using supplements. Even going up to 50% a week would be cheaper, which for me would be about 50 gallons per change. <Ok...I am a big water change fanatic, but I think I'd limit them to 10 percent per week, 15-25 percent max. If it were me, I agree with you that it's a better idea to utilize water changes to "replenish" trace elements, etc., but 50% water changes would be a rather unnecessary extravagance, IMO. I wonder how much supplementation that you'd use in a 100 gallon tank to make changing 50 gallons of water a practical solution!> The idea here, of course, is to bring in all needed major & trace substances during these changes, in addition to the benefit of flushing away the bad nitrogen guys and what have you. I got this idea from my LFS, who perform weekly 90% changes on some of their reef tanks and don't bother with any supplementation or even skimming. <Again, I love water changes, but I have to question that philosophy. Even public aquariums with semi-open systems utilize protein skimming...It's your first line of defense for many potential water problems. However, the concept of massive water changes is interesting...But there are other potential problems, such as the trauma to animals, if performed in a lax matter> Of course, reading through the literature such as Fenner's TCMA, advice is given against doing too big of a water change due to the shock it may incur on your critters...and the loss of some beneficial stuff, like calming pheromones. <I agree with the issue of potential shock, as well, if parameters are not consistent> I'd like to get some feedback on this topic (25%-50% weekly changes), and perhaps some more info. on what negative things can happen from this? I assume that I will keep using a high-quality mix that gets nailed every time in terms of matching the tank's salinity, pH and temp....and that the fresh mixing water is as pure as possible. Thanks so much! SLC <Well, my concerns are mainly based upon the practicality and affordability of such massive changes...It's a neat concept. As Anthony quotes "dilution is the solution to pollution"! I like the idea, in theory-I just cannot imagine the average hobbyist bearing the expense. If you can afford it- and if you can do it right (keeping things stable and consistent), then go for it and keep us very well informed as to your progress! Good luck! Regards, Scott F>

Major Water Change??? Actually algae control, gaining sufficient knowledge 7/14/05 Hello <Hi there> First and foremost, thank you for hosting such and excellent site, very informative.  I have an issue regarding green water in my saltwater aquarium.  I had this issue once before and my local pet store determined that my water was fine, but, I was not supplying my live rock with a calcium buffer.  I purchased the Kent Marine Tech CB Buffers and the green water went away within two weeks.  Here are the specifics on my tank setup: 29 Gallon Saltwater Tank 1 X 65W 10,000K Daylight & 460nm Actinic w/ Lunar Light Powercompact Remora Aqua C skimmer 2 - Penguin 550 Powerheads at opposing corners 30lbs of Live Rock pH 8.4 ammonia = 0 nitrites = 0 nitrates = 0 alkalinity = normal (no numbers on the test strip) calcium = 420ppm When the water went green this last time I had a Prizm Skimmer in service, that got replaced by the Remora after reading your opinion on the Prizm. Also, I had only one powerhead before reading your website.  Plus I have made weekly 20% water changes.  The water has cleared some but you can hardly make out the live rock, yes, it's that bad.  The residents of the tank are a yellow watchman goby, lawnmower blenny, flame Hawkfish, fire clownfish, sea cucumber, 8 hermit crabs, 4 turbo grazers and an anemone.   Before reading your site, I had made the error of resting a piece of live rock against the glass.  I understand now that this is affecting circulation throughout the tank.  My problem is, since I can't see into the tank clearly enough, I don't want to move around the live rock.  My question is, do I proceed with a major water change, i.e. 50% so that I can at least do that? <Unless there was some compelling reason, I would not (ever) change more than 25% of the water in an established system. Much more likelihood of trouble...> Thank you for your help John Fey <John... please read here re Algae Control: http://www.wetwebmedia.com/algaeconMar.htm and the linked files above... till you formulate a plan of action here... I would check for phosphate, perhaps employ a chemical filtrant... consider adding a sump/refugium, biological control means... Bob Fenner>

A MORE Perfect Water Change Routine! 8/24/05 All, <Hi there! Scott F. here tonight!> I read your article on the 'perfect' water change regimen, and now have a question. The article suggested 5% water changes twice weekly, but it also implied that this was in conjunction with a skimmer. <Yep...I highly recommended combo, IMO!> So, if I am running a skimmerless nano (20L), should I do larger changes at the same interval? I currently change 5 gal NSW twice weekly, your system would have me changing only 1 gal twice weekly. My corals are thriving and my fish (Banggai cardinals) are breeding, so maybe I am answering my own question here, but just wanted to get a professional opinion about the 'skimmerless' issue. Thanks, James <Good question, James. Of course, being the water change fanatic that I am, I'll recommend sticking with the water change regimen that you already employ! In my opinion, it's all about consistency and observation. Your 2- 5 gallon water changes are working well in your system, and I certainly would not reduce them if you're happy with the results. As you've seen us state time and again here on WWM, nano reef tanks require a much higher level of attention to husbandry than larger tanks, because of their inherent instability, so I like your idea of the large water changes. I like the idea of smaller, more frequent water changes, because they help remove dissolved organics before they have a chance to accumulate and degrade the water quality, which is why I wrote the article. It's so easy and beneficial-and it becomes a part of your tank routine very quickly. In the absence of a skimmer, your water change routine is your best ally, and I'm happy to hear that you're employing it successfully! Best of luck to you! Regards, Scott F.>

Water Change Schedule Hello, I have a 75 gallon saltwater fish only tank. The actual water volume is right at 65 gallons.  My substrate is crushed coral and I have no live rock.  Please tell me what percentage of water I should change each week.  Thank You, James <Howdy James,  there is no set rule on water changes, it is a lot like the other aspects of this hobby, what you need (or need to do in this case) is affected by what you have already or what you plan to keep.  If your tank is overcrowded, or has a bunch of messy eaters you will need to perform larger water changes, or more frequent water changes.  Your best bet is to test your water frequently and take this information to adjust your water change schedule.  I like to change 1/4 of my tank volume weekly.  Best Regards, Gage>

The 5% Solution? (Frequent Small Water Changes) Hi guys, <Hey there! Scott F. with you today!> For the second time today! It's RESEARCH MONDAY for me apparently:-)I was in one of my LFS. During the course of conversation I mentioned that I make 5% weekly to 20% bi weekly  water changes. He said that routine was not as effective as a Monthly 50% change. All this is assuming tank is healthy and balanced Here's his logic: He said: say you have "100 ppm's of Nitrates" just for an easy number, in the water when you change it. By changing 50% of the water monthly you eliminate more dangerous elements such as Ammonia, Nitrates etc. He said you eliminated 50% of those "100" when you did the big water change. He said if you are doing several small water changes over the month you are not eliminating as much waste and toxins. <Let's look at this his way...If your nitrates are already 100ppm, of course larger changes are required to dilute the nitrate. I think he's missing the point: The reason of the smaller, frequent water changes is to keep nitrate and other organics from ever accumulating in the first place! I'll be the first to admit that two 5% water changes per week are not going to reduce outrageously high levels of dissolved organics. If you start out right with diligent husbandry techniques, you won't need to do massive, potentially traumatic water changes at longer intervals> I thought yes, but your nitrates, ammonias etc are not always at their highest levels when you decide on a monthly routine.  I am still in the several small/month camp. <Well, I think that you are in the right camp...I think that if more people embraced this technique, they would see more consistent, high quality water conditions, and would find themselves having to take a lot less "corrective" actions, or using a lot fewer "additives" to keep their systems in good shape.> I am no scientist (that's my husband's area of expertise) but it just didn't seem quite as simple as the sales guy wanted it to be. <It isn't! LOL> I am trying to not to be swayed from what has been working for me. What is you argument for the several or against the large monthly? <As outlined above...To me, one of the most important things that we can do in closed systems is to provide stability. Stability involves water changes that keep pace with the organic waste production in your system. Check out this link: http://www.wetwebmedia.com/scottsh2ochgart.htm If anyone is skeptical, I'd encourage them to set up two identical systems, and change the water in one of them twice weekly at 5%, and the other once per month, at a larger volume...You'll see the difference for yourself, believe me. I've done this!> Thanks Again for all you help! Thanks, C.Evans <Any time! And never hesitate to question any idea...That's how great new ideas are born! Regards, Scott F> - Small Water Changes - Why are smaller more frequent water changes better than one larger one a month?  Thanks again, James <Please read here: http://www.wetwebmedia.com/scottsh2ochgart.htm Cheers, J -- >

Scott's H2O Method Aloha, Bob! <Hey Scotter!> I felt that a number of our readers would benefit from a better description of the theory behind my oft-recommended twice-weekly water change technique. I think that quite a few people are embracing this idea with great success...Or, at least humoring me for my constant clamoring to perform them! <Great> Attached please find a brief piece that I composed summarizing this concept. Perhaps it might make a good addition to the FAQs on maintenance? <Mmm, can't "open"... can/will you resend either just on this tray... or maybe as a "Word" or RTF formatted text?> Hope all is well with you and Di.  Looking forward to being back "home in the Islands", myself  later this summer...If our paths don't cross in Kona, perhaps I'll see you and Anthony in LA next month? <Do make it known if you can use the place here (about 1,300 ft. Mauka of Kailua. And let's plan on meeting altogether if you'd like... on a day when Anthony is in southern Cal. Think we're planning on a day to L.A. to pimp books...> Keep it wet! Scott F. <Yowzah! See you soon. Bob F>

Water changes and trace elements 7/15/03 What percentage of water should I change weekly.  Right now I am changing 5 gallons a week (65% actual water volume). <I don't follow your math for this 75 gallon tank. At any rate... the water change schedule will be dictated largely by water quality and the bio-load. Somewhere around 15-20% weekly for a minimum would be nice though> Also, wouldn't the water change only replenish depleted trace elements in the amount of water I change?   <correct... but we cannot/should not assume that all of the trace elements in the remaining water are depleted. The rate of uptake will vary considerably> It wouldn't help the rest of the tank would it?   <as per above... its only an issue if the demand exceeds the pool of reserve of said elements in the remaining water (not likely with a light/proper bio-load and regular water changes)> Thanks again.  James <best regards, Anthony>

Re: Reef tank (diligence, maintenance) Hey Bob, My tank seems to be under better control. My maze brain is looking healthier and the long tentacle is better, but my gravity reading is quite high about 1.025 to 1.026. I read some articles on your website but couldn't find what the best gravity range should be, <This is right about right... do check on the accuracy and precision of your specific gravity tester though... and there is a section on spg on the marine index: http://wetwebmedia.com/spg_salinity.htm> maybe I wasn't look in the right place.  <Amazing... don't know how we could make the arrangement of materials on WWM any more logical, accessible... did you consider using the Google search tool there? Try inserting the words "specific gravity", "salinity"...> Also once a month I change about 10 gallons of sea water in my 30 gallon, should I be doing more? <See the section on "Water Changes"... better to do five gallons twice a month> Also when ever I change my filter cartridge on my Eclipse bio-wheel 3 hood it seems like waste matter enters the tank even when I turn off the pump, replace the filter, and then turn it back on. <Yes, design defect/user failure, but no big deal> Do I even need a filtration system for such a small tank or is my skimmer (sea clone) good enough? <You need a filtration system> Again thanks for all the advise, you have kept me sane this week. Have a great weekend. Thanks Jason <Keep studying my friend. Bob Fenner>

Water changes Hello again, friend. I hope this letter finds you well. <Yes, thank you.> I have a question regarding water changes.. I have a 75 gallon tank that I've been doing a 10 gallon weekly water change on since I got it.. I'm currently considering adding a quarantine tank underneath the tank, and it would knock out some of the space I use for my 5 gallon buckets to do water changes.. my question is this.. would 5 gallons every week still be enough? <Possibly... but ten every two weeks would be better...> Or should I relocate my buckets to a storage closet and keep it up with 10? <This would be the route I would go> Also, for a 10 gallon quarantine tank.. I mentioned I have a Prizm skimmer.. would this be enough filtration (provided there is some live rock in the quarantine tank) or will I need to add more?  <S/b fine... might add a small outside power filter or inside sponge filter (air or power)> Other than that my quarantine tank will just need a heater/thermometer (I wouldn't think any powerheads as the Prizm is supposed to be for larger sized tanks and should move the water plenty) Please do let me know if I've forgotten any thing! Thanks again from Atlanta <Lighting for the live rock, a timer... Bob Fenner> Bill Hammond

Water changes Hello Mr. Fenner, <<Jason C here, doing my best Bob Fenner impersonation, practicing for his upcoming dive trip, hope you don't mind.>> I hope everything is going well for you. I have been reading your web site for a few months now and enjoy very much. I have been reading about fish and corals more then anything. Today I read about water changes and I am wondering if I have been doing something very wrong. I have 75 gallons and I change 5 gallon each week. I have a fair dusting of diatom on my gravel. When I do the water change I run the hose over the top of the gravel (not down into it) to clean up this algae. I run over the whole area of sand that is not taken by my LR. Is this okay to do? I am wondering if I am harming my balance by taking this algae from the gravel as often as I do. Or was the point in your writings not to go down into the gravel all over. I hope you are understanding what I mean. :) <<Your water changing practices, including the gravel cleaning are all plenty adequate; certainly no harm being caused by taking the diatoms off the top. You might want to clean the gravel more thoroughly once a month or so...>> Thank you for your time to read this. I hope that you are able to write back. I will look forward to hearing from you. Carlos <<Absolutely my pleasure. Cheers - J>>

Water changes Bob, I have a 46 gallon tank with 45 lb. Live Rock. I have (2) peppermint shrimp and (1) green Chromis and (1) clownfish (2) turbo snails and (1) blue Linckia. I remove approx. 4 gallon of saltwater every week(8.7%). Does this seem good enough as far as water changes go or should I do a water change every 2 weeks? <Weekly is better for your tank.> Is Baking Soda the best solution for low Alk. or is just a temporary fix? <There are better commercial preparations, such as Seachem Reef Builder.> Well Bob you haven't let me down with any of the information you have give me. Thanks <Glad to hear you have found the information useful. -Steven Pro>

Water changes Is it harmful to do water changes too often or in too large of a quantity? I have consistently have had a problem with brown rusty film on the inside of my tank & on the substrate. I clean it off and it shows up again pretty heavily within a week I know you are supposed to get that within the first 2 months of a new tank. My tank is 7 months old ( 72 gal) and I chg 5 gals once a week. I was wondering if that is to much and that my tank keeps recycling? <Five gallons in a 72 gal. system... once a week... actually may not be enough. Please read: http://www.wetwebmedia.com/water.htm and the FAQs beyond> One other problem I have that I can seem to get rid of is very small air bubbles. When I shut off the wet/dry they seem to go away when there is no water movement- I have tried putting an elbow joint on my water pump intake and have tried inserting foam sponges in the return section of the wet/dry. Any other suggestions. Thanks <Yes. Please go to the homepage of WWM: www.WetWebMedia.com and use the Google Search at the bottom with the terms "bubbles", "wet-dry"... and read the areas you're led to. Bob Fenner>

Water Changes Hi, I have a 50 gal., fish only tank. I mix my water in a separate 25 gal. container with a power head and heater and have been leaving it for a week or more between changes; works great! <Good protocol. About same as mine. Please read: http://www.wetwebmedia.com/water4maruse.htm> Lately, I've been changing 2 gals. every 2-3 days to try to prevent any spikes in the quality of my water between major cleaning/changes. In your opinion, will the replacing of the 2 gals. and using it again so soon have any adverse effects? If so, any opinions on how to handle this? <S/b fine. Please see: http://www.wetwebmedia.com/water.htm and the FAQs beyond> I know the quantities I've mentioned may sound a little trivial, but I've had quality problems in the past which have lost me some of my favorite fish and water quality is #1 on my list of priorities for problem prevention. Thanks, Rich <Best to shy on the side of conservativeness here. Bob Fenner>

Become a Sponsor Features:
Daily FAQs FW Daily FAQs SW Pix of the Day FW Pix of the Day New On WWM
Helpful Links Hobbyist Forum Calendars Admin Index Cover Images
Featured Sponsors: