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FAQs About Water Changes for Marine Systems: Techniques

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, Frequency/Amount, Automation, Trouble/shooting, & Water Top-Off Systems, Evaporation/Water Make-Up, Treating Tapwater Marine Water QualityMarine Plumbing

Water change, water line ?  1/6/11
Hello and Happy New Year,
<And to you>
I hope all is going well. I have a few SPS corals in my system that are starting to grow closer to the water level. I am afraid in the near future that the corals will be above the water line during the period of water
changes. Is this a problem?
<Mmm, not so much>
If so, what should I do?
<Mmm, either trim them (perhaps mount as frags, sell, give to others; or move these colonies a bit lower in the water column. Leaving all as is will result in their "topping off" at the air-water interface with growth. Otherwise, periodic, minutes exposure is not likely to prove problematical. As you likely know, many hard corals are air-exposed at times in the wild. I might turn your lights down/off during such exposure>
As always,
Thank you,
<Welcome. Bob Fenner>
Re: Water change, water line ?  1/6/11
Thank you very much, I figured that there would not be any issues but I always check with you guys first.
<Certainly welcome. BobF>

Need Bob Fenner's Expertise!!! Water change, synthetic salt mix prep.  -- 01/03/10
Hi Bob & Crew!!! I have opened a can of worms with the following thread after quoting Bob Fenner & I would love if Bob could read the following thread & posts & give us as much detailed explanation as possible....Thanks....
Sue Brown http://www.reefcentral.com/forums/showthread.php?t=1767456
<Hi Sue, and thank you for sending this along. Have read through the thread, and will try/proffer a bit more, albeit still likely too vague input re this issue: The suggested addition of some "old water" into new that is being prepared for water changes in an established system. First though, I do encourage anyone "really" interested to try experimenting... adding and not... and measuring whatever characteristic/s they might... ORP, DO, BOD... most anything... even if there's time, sufficient replicate systems (can be very small) various bioassays with small life... The overall benefit of such mixing of new and old water is to discount the chemical and physical "new-ness" of the change-out water. How to put this... tap/mains water is proving more variable and synthetic salt mixes much more so in recent years. Blending in the life in the new water days ahead will generally help to reduce/dampen these potential "difference" effects. Oh, and I do want to mention that our captive systems do generally have high (though also variable) concentrations of microbial life... often orders of 10 to the seventh per milliliter... even with "super filtration"; skimming, UV, ozone use... Again, this can be measured... through a few means. Simplest, a "high power" microscope and counting slide (e.g. hemocytometer). The vast majority of folks/aquarists skipping the "extra step" of adding old water to new are going to be fine, but I still encourage the practice; if nothing else, I have found it is a good/important reminder/stimulant to urging further consideration as to what one is up to. Cheers, Bob Fenner> 

Newbie question: Water changes with a sump 12/14/2009
<Hi Laurie.>
I am a newbie to salt water aquariums and need some information on maintenance.
<Welcome to the madness.>
During water changes with a reef tank do you close off the upper aquarium and work on the sump, draining cleaning etc , and then once the sump is refilled turn the vales back on to the top tank? or are you suppose to clean the sump with the top tank running and still draining into the sump?
<It is a matter of personal preference, so you get to read about how I do it. I close the valves on my drains and turn off the pump. I then do my water change in the main tank. Then, I drain out my sump and clean that. I refill both the tank and the sump, and start everything back up again.
You can read more about plumbing here:
http://www.wetwebmedia.com/marsetupindex2.htm Scroll down to the sumps and plumbing section. Lots of articles there on how to set it up for easy maintenance.>

Stirring Substrate With Water Changes 4/9/08 Good Evening Crew! <Good eve Gans.> I have a crushed coral substrate. Before I do water changes I stir up the substrate with a small power head to get all the junk out which then gets collected in the skimmer. Is this a good thing to do? <Yes, I would with this substrate too.> I heard the substrate houses a lot of beneficial organisms. Will doing something stirring up the substrate harm then in anyway? <No, leaving the substrate alone applies more to sandy substrates. In this case you may even want to gravel vacuum with your water changes to siphon out the maximum amount of detritus.> Cheers Gans <Best regards, Scott V.>

Water Change Technique 3/15/07 Dear WetWeb Media <Hello> After I got done reading your last answer you sent me. I got to thinking about if I was even changing water and cleaning the tank the right way. I have this question for you. <Ok> When you do water changes and clean the filter sock that I have in my sump, do you shut down the system, meaning the pumps while you do this? <I do.> I hope this is not a crazy question for you. <Not at all.. I just don't know the answer to it 100% I think I'm right but I'm wrong a lot more than I'm right? <Me too.> Because I have been turning the pump off when I do water changes I just thought that was common sense. <Is to me, less chance of burning something out that way.> Thank you for your time answering my 1000's of questions. Jeff <Welcome> <Chris>

Re: Everything going bad 01/24/2008 Thanks so much for the responses. <<Hello, Andrew again, thank you for the follow up>> I broke down and got a R/O system because I got sick of driving to the LFS to buy 5 gallon jugs of water (this isn't a cheap hobby by the way). I've tried to read through the faqs on water for marine systems and I've got some better understanding on how to handle water, but I've still got some questions regarding storage and top off. <<No problem, we shall get these cleared up for you today>> First off do I need to worry about water top offs on a 55 gal tank with sump if I'm doing weekly 10% water changes? Is this eventually going to raise my specific gravity due to evaporation, or will the water changes take care of that? <<Yes you do need to top off the water. If you don't, the Sg of the tank will rise because the water evapourates, but the salt stays behind>> If my SG does start getting away from where I want it what's the best way to bring it back? By adding fresh water, or lower SG water changes? <<If your SG is getting high, then only add RO water to bring this back to acceptable levels>> If I do need to do top offs in small amounts can I just use straight RO water into the sump as long as the temperature is close? Or do I have to aerate, heat and let it sit over night? (I'm trying to build good habits for a reef tank down the road, but I don't want to spend hours each night keeping this thing going) <<As long as the temp is average of the top off water, adding it to the sump in small amounts is fine. Maybe consider purchasing/setting up an Auto-Top off unit>> Second, when I'm "aging" water should I age it as fresh water, or after I've aerated, heated and added salt mix? <<I do it all in one go. I turn on the powerhead and heater, add the weighted out salt to the water, leave for 24 hours. Check levels and adjust over the next 24 hours. Then all is good and ready to use>> Finally, do I only need to aerate 24 hours prior to water change, or once it's been aerated can I store it like that? I'm just trying to come up with a checklist of things I need to do. <<You need it aerated 24 hours at least, I prefer 48 hours personally, before use. This gives the water time to settle, and get to the right temperature and SG to level>> I have a small house and storing multiple trashcans full of water is going to be difficult for me, plus the setup of my RO water system will make it very time consuming to fill the trashcan so I'd like to get enough water to do multiple water changes if possible. *** Kind of like this... ** Run R/O water into Rubbermaid can Aerate with powerhead and heat over night (longer?) Add salt mix to get up to 1.023 (what I'm currently at with FOWLR system) Add buffer as needed Do water change ...store water for a week Aerate and heat overnight Do water change Repeat <<Yes, that sounds fine. I used to be in a similar situation. I had one trashcan ( waste bin here in the UK ;) ) always full of RO water. When it was coming time for water change I would remove the required amount of water to a separate trashcan and add the required salt, mix etc etc. Then store away the can after the water change till next time. This way, you don't have lots of saltwater sitting in a trash can without movement and heat>> Is that kind of right or should I store it fresh after aerating and heating for top offs and only add salt/buffer 24 hours prior to water change in smaller batches. <<See response above>> Finally some non-water questions: <<Oh good>> For my Aiptasia problem they're really only bad on a couple of rocks (maybe 2 or 3 out of 10 or so). If I pulled these rocks and gave them a real good cleaning would it affect the bio filter enough to make a difference? How long does it normally take for dead rock to become live rock? <<A good simple solution for Aiptasia removal is to fill a syringe up with boiling water, and blast the Aiptasia directly, watch it melt. Dead rock to live rock really depends on the amount of live rock in the tank to seed the dead. Can be anywhere from a couple months, to 6 - 8 month, a bit too open-ended to answer more specifically>> What's the best time to treat the Aiptasia with Kalkwasser and scrape algae/bacteria to reduce stress on the fish? Right before/after a water change, far from a water change? At night when they go into hiding? (I forgot to mention this earlier, but one of my gobies ate a big blob of Kalkwasser paste after I was treating the Aiptasia which may have led to his disappearance) <<This will certainly not of helped the fishes stomache..>> Sorry about all the questions. Chad <<Thanks for all the questions, hope this helps. Please shout back if you need some more clarity or more questions. Thanks, A Nixon>> Corals out of water - 9/14/05 Hi Mr. Fenner! <Paul here to help> Thanks for the last reply! I only forgot to ask about SPS and the water line. I know one should initially place corals 4" below surface and that is what I did. My Pocillopora is now noticeably growing. When I do my weekly water change it gets very close to the lowered water line. Within months I wont be able to do water changes without having part of the coral emerged. So is it bad to have a SPS coral (Pocillopora and Montipora species) partly out of the water for (at the worse) 30 minutes each week? <OK. Well, I have the exact same issue with the exact same corals. The short answer is for a short time, I would say I haven't experienced any issues with bleaching or color problems or anything of that nature. Any longer than that though, I would have to think you might see some issues. Now all this depends on the water replacement, health of the coral, lights on or off etc. I use raw natural seawater from Monterey Bay, I feed my tank a mish mash of Mysid shrimp, Cyclop-eeze, enriched brine, and other stuff, and I do try to water changes with the lights on but not always. Of course there are many more factors that I am sure could be an issue and/or might affect the corals ability to be above water for a short time. For some corals in the surf zone this isn't an issue, but the corals you mention aren't technically surf zone corals. Try and see. Let me know what you find. ~Paul> Thanks again!!! Dominique

SW gravel vacuuming 10/10/05 Hi Again Mr. Fenner, I read on WWM about the cleaning of live sand during a water change. Again I do have an undergravel filter in there and whether or not it's actually doing anything, I'd like to keep it clean so that I don't encounter the negative factors of the UG filter. So, here's what I found Re: Live Sand.  I was hoping that I would be able use the Python and clean the tank better. <You can... but "cleanliness is not sterility"... you don't want to "clean" the substrate too well> I was thinking of just stirring the sand and with a fine net removing the particles that come up out of the sand but I was told that would kill bacteria and produce more nitrate is this true? <No... consider the alternatives... and their results. Bob Fenner> So basically are you saying that it is OK to stir up the sand on the substrate to remove debris without killing nitrifying bacteria? <Mmm, it's okay, just don't be too fastidious> I have a cleaner shrimp and that star fish and I don't know if they  help with the cleaning process. Besides I'm not sure if any small particulate got trapped in the sand from the UG filter or not, and if so I want to get it out. Being said, if I stir up the sand and all the gunk goes everywhere, then what, am I responsible for trying to get it all out or will it just settle back down and be taken care of  by the inverts?  Forgive me for being naive in this matter. I have only worked with crushed coral in the past in which I just siphoned and  most of the stuff trapped in the substrate just slipped up into the hose. Now the sand goes right with the water and debris. I know I shouldn't have an UG filter in my tank especially with reef sand, but it's there, and I really don't want to cause a disaster removing it,  <You won't... you can siphon it out... replace it, abandon the UG filters, just leave the plates in place...> so is there anything that you are able to add in order for me to keep it from potentially causing any harm? Again, it seems like a little bit of a different story with live sand, than with gravel or crushed coral.  I know I should search more and I am trying, but I trust and appreciate your direct advice. Thanks again for everything! -Jon <Better for you to search, come to understand the many related issues, side-issues... the "logic" behind WWM is this exactly... to help people gain insights into a/the "big picture"... not really "just what they seemingly want to know right now". Cheers, Bob Fenner> <<Use our Google bar, search on "Marina, deep sand bed, vacuum/ing" and you should find the technique I learned at the Long Beach Aquarium.>> 

When It's Time To Change... (Water, that is!) Thank you for all the help you guys provide as well as the very informative website you guys put together.  Forgive me if my questions seem too dumb or stupid which is probably why I can't find these in the FAQs.  <No such thing as a stupid question! Only a stupid answer! Well- maybe not! Scott F with you today!> My questions are in regards to water changes. 1.When aquarists do water changes, does that mean just siphoning the water out or actually vacuuming the gravel or substrate? <Well-yes-and-no! How's that? A water change by definition (mine!) is an exchange of existing tank water for newly prepared water of the same quantity. While it's a good practice to siphon out detritus wherever it is found in the tank, it is not mandatory to vacuum the substrate to accomplish a successful water change. In fact, overly aggressive substrate siphoning in (deep) sand beds can damage the very processes that you're trying to foster there!> 2.When doing water changes is it best to siphon water out of the main tank or the sump?  Or does it matter? <A good question. Since the water in the sump flows through the sump, you are simply removing  water from a different location in the same system! If you are planning on removing detritus from the main tank, then take the water from there. Otherwise, IMO, it's perfectly okay to remove water from the sump (of course, I'd make  sure that pumps are off to avoid damaging them. In fact, detritus does accumulate in sumps, so it's not a bad idea to do this once in a while>     3. This question kind of relates to #1.  For the people who have reef tanks with deep aquariums and/or intricate light setups in the canopy, how or do they vacuum their substrate?  With all the rocks in the way in the reef tank, deep tanks making it tough for short people, and/or heavy canopies they must take off, it would seem too laborious for them to do especially if they do bi-weekly water changes.  Possibly siphon water one week and vacuum gravel another? <Another good question! I just ordered a new canopy for this very reason on my main system! It's a real pain getting into a tank with limited access, so lots of aquarists get it right (the second or third try, sometimes!) and design and construct canopies that make life (and maintenance) easier! Your idea is just fine. In the long run, it's still a good idea to obtain or build a lighting system and canopy that allows free access to the tank. The thought is, that the easier the access, the more likely us lazy humans are to do regular maintenance!> 4. A question off the topic.  Will we have an electronic machine in the near future, that has the ability to read multiple things?  (i.e. salinity, ph, alkalinity, medicine levels, etc.) Thank you for reading my questions. <Absolutely! In fact, some products already exist, such as the Aquadyne line of monitors/controllers, that can monitor, report, and control various pieces of equipment to adjust parameters and alert the aquarist of changes in the system. I have no doubt that, as technology progresses, there will be even more advances in the state-of-the-art! What a cool hobby! What a great time to be alive! I'm stoked! Feel free to contact us any time! Regards, Scott F>

I recently went to a well known marine fish store in my area and was talking to an employee about water changes. she told me I was doing it wrong because I wasn't "vacuuming" the bottom substrate. I was under the impression that you only did this kind of water change with fresh water fish. my friend and I did this vacuuming change to his tank and the water out of the gravel was dark brown. did we do the right thing? should I do this from now on? my substrate is crushed coral. I was previously doing about a 10 gallon water change every two weeks on a 55 gallon tank. filtration is 2 Fluval 403's, UV sterilizer, protein skimmer, 1 bio-wheel, 50 lbs of live rock. >> I'm a fan of the periodic "gravel vacuuming and/or stirring" philosophy... I would do this with your regular water changes... but no more than half the tank at an interval (the left side on the mid-month, right at the end of the month...). To keep the system in "dynamic equilibrium" (one of my favorite oxymorons)... Bob Fenner

Many roads to aquarium success I have two small (46g & 30g) tanks with live sand and live rock. When the water levels get low, I add just a gallon of straight distilled water. <Reverse osmosis would be fine, cheaper> I don't have regular stand-by salt water mixed and ready to go. When I do my 5% water changes every three weeks then I use saltwater that I make fresh. Is it harmful to a system to be just dumping in water like that? <Not very harmful... five percent is not much> I have seen no visible signs of harm, my tanks have been up and running for almost a year with no livestock problems. I run powerheads and powerful skimmers only. <Your success is all that is important, not specific methodologies. Bob Fenner>

Water change and septic Robert, I live in the country and have an aerobic/aerated septic system (doesn't use a leach field, sprays out like a sprinkler system). It is suppose to process approx 3,000 gal a month. Would it be a problem to the septic if I flushed my 10 gallons a week water change? <Mmm, ten gallons out of a few thousand should be fine> If so, would it be okay to pour out on the lawn or would it kill the grass? I need somewhere to dispose of it, any other ideas if these don't work. Thanks, I reread your book consistently. <More than me!> Lee parker <Be chatting my friend. Bob Fenner>

Sand bed cleaning I got a question regarding hydro-cleaning a sand bed. I've got a 125gal tank with about 5-6in of fine (sugar sized) sand. I haven't vacuumed it for about three months because I've been attempting to 'automate' the process by employing a highly diverse and strong fleet of detritivores (spaghetti worms, amphipods, copepods, Mysid, cucumbers, micro stars, brittle/serpent). regardless of how great the system sounds on paper it just doesn't work well enough. so no am stuck with ultra fine sand that needs to be hydro-cleaned.  <Or stirred perhaps... not shaken, call me Bond> can you recommend or point me to a place where I could get a cleaner designed to get waste and not sand? I've heard that they exist, but are pretty expensive. id rather DIY the vac. <This can be done... easy enough to build a large enough diameter gravel vacuum... that you can "fine tune" the flow with so you don't suck out the fine substrate...> anyways am struggling with a dissolved organics issue and am left with few options. <Why?> am doing frequent, large water changes 50% every week <This is too much> and I vacuum out large patches of Cyanobacteria and other slimes/algae. so at least the organics locked in them are out of the system.  <99.9 some percent water...> also I harvest my Caulerpa tank regularly, sadly that's the only thing that is enjoying the sewage issue. oh, and the bio load exerted by my livestock is medium-low. god, I hate vacuuming tanks... it looks like my quest for a (mostly) carefree system got me into trouble. thanks Jon Trowbridge <Time to investigate your options a bit more... do post your query, situation on our chatforum: http://talk.wetwebfotos.com/ Bob Fenner>

First Water Change Bob, <Steven Pro this evening.> I have been reading your articles and find them extremely helpful. I have a quick question you: I have a new 40 gal. saltwater reef tank w/ 40 pounds of live rock (no fish yet). It has been cycling for a week and a half. I did a test on it and found that the cycle has completed, 0ppm nitrite, 0ppm ammonia, ph8.3, but my nitrate are up above 60ppm. Now for the question: I am ready (I think?) for the first water change and am petrified. I have setup a 5 gallon bucket (with city tap water), an air stone, added the salt, buffer and Prime (for the chlorine in the city water). Everything looks good. How long should I leave the change water set before pouring it into the tank? 24 hours? 48 hours? <24 hours is plenty of time> Also, when removing the water out of the tank, should I "dig" into the pebble coral on the bottom or should I just remove it from wherever? <Yes, you do want to remove any detritus that has settled from your liverock into the gravel substrate.> Any help would be great !! as I am biting my nails for this first step. Gregory Hustead <Take it easy and enjoy you aquarium. -Steven Pro> Maintenance Questions Pretty new to the aquarium hobby, but have been at it about 8 months now. Was told to wait a while before I vacuum the substrate, so I have. Now, I realize that when I try to vacuum the base of the tank, all of my live sand goes into the hose/snake as well. <Mmm, give it a preliminary stir with a wood or plastic dowel (to break up the chunks!) and devise or buy a siphon with an "exploded end" (we used to make our own out of plastic bottles with the bottom cut off and a good length of tubing attached to the narrow end...). Such "funnels" allow you to stir up the bottom, remove the muck, but leave the substrate behind> Looking for a trick to avoid this from happening. Was also wondering how long I should wait before I change the white and blue pad in my canister filter. (the water is still crystal clear, I believe due to the protein skimmer) <Do this on at least a weekly basis... good to remove the grunge there before it dissolves, returns nutrients to the water... fueling algae growth et. al.> Love the web site. Thanks, Tim Gauen <Thank you, Bob Fenner>

Maintenance Questions Pretty new to the aquarium hobby, but have been at it about 8 months now. Was told to wait a while before I vacuum the substrate, so I have. Now, I realize that when I try to vacuum the base of the tank, all of my live sand goes into the hose/snake as well. Looking for a trick to avoid this from happening. <If you have a DSB, you should not need to gravel siphon it. Occasionally some detritus might settle there, but you should not insert the siphon into the sand.> Was also wondering how long I should wait before I change the white and blue pad in my canister filter. The water is still crystal clear, I believe due to the protein skimmer. <Depends on the brand and model, but generally every 1-3 months.> Love the web site. Thanks, Tim Gauen <You are welcome. -Steven Pro>

Water Changes Hello again, Thanks for the feedback on my previous question. I was reading about water changes on your site. Thanks for taking the time to organize all of this for us. I have a water softener at home, but I didn't come across many FAQ's concerning softeners. <One word of caution concerning water softeners. I have read one report of someone using a brand of salt and not noticing that the salt included compounds that alleged to clean the water softener. These compounds, whatever they were, were toxic to fish.> In an article, Bob states that tap water is just fine. <For some applications> Please give feedback to a possible way of preparing water for a water change. I have a 55g tank and currently doing 5-10% changes every week, depending on how much water I feel like carry over to the tank. Here's my thought: What if I : - filled a ten gallon bucket with straight tap water; water is "softened" but unfiltered - I add no "de-chlorinizers", is that a word? <They are called dechlorinaters and I would use them.> - I put an air stone in overnight - Next day, I add Kent Superbuffer. Is this the kind of buffer I need to add? <It should be fine.> Can I just add baking soda, and if so, how much per gallon is safe? <Use test kits to confirm the pH and alkalinity.> - I continue aerating for a few hours - I then add Instant Ocean salt, mix, and wait a few hours before adding to tank <More like 24 hours.> Does this sound like a reasonable plan? <See notes above.> Up to now, I've just either been mixing salt with DI water immediately, then pouring it into tank without waiting; <This can be dangerous.> or I've been mixing salt and water immediately, then waiting overnight to add it. Neither of my current ways seems appropriate, based on the info on the site. Please help me be a better fish/reef keeper. <My strong preference is to use DI water. Aerate and heat that water for 24 hours. Then add the salt mix and wait another 24 hours. At that point, test for pH and alkalinity and adjust as needed. In another 24 hours, it is ready for use.> Thank you, Randy M. Yniguez, MA <You are welcome. -Steven Pro>

Mixed Up About Salt Mixing Hi guys, couple questions about adding salt. <Sure!> I am using Tropic Marin and was wondering how much salt per gallon of water should be adding when making up new water?  I have been adding 1/2 cup and it seems to be to much. < I am a Tropic Marin user, too. I use about 2 cups per 5 gallons, and that seems to yield a s.g. of 1.024-1.025 at about 79 degrees F.> Last thing I have been mixing about 20 gallons at a time in a Rubbermaid trash can...RO/DI water.. let aerate and heat for a day then I add Seachem buffers.  I then add the salt. <Great procedure!> Question is......when I add the salt to can it is clear (water) but after 3 to 5 days the water is still very cloudy, I continue to aerate the whole time, but it doesn't seem to ever clear out.. then when I do use the water there is a thick white film on the sides of the can that I have to rub/scrub the clean off.  The water in the tank does clear up though.  What do you think?  Thanks a lot Bryan <Good observation, Bryan. I notice this phenomenon at times, too. I think that it probably has something to do with some of the salt or buffer components not dissolving completely into the water, or perhaps, even falling out of solution.... As long as the water mixes up to the correct specific gravity, pH, and alkalinity, I would not be overly concerned. Keep up those water changes! Regards, Scott F>  

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