Water Changes--What's the "standard" percentage?

[deehz]

Just as it states and I hope that many chime in from the club and outside the club. I have read and firmly believe in water changes.

But what is the "standard" percentage? I usually due my water changes every other week, about 10-15 gallons. However if the "standard" percentage is 5%, then does this mean that I can get away with doing water changes every other month? According to the "standard", you are supposed to do at least bare minimum, 5% water change to your system every week. 10% is better.

So take my system for example: 34 gallons of water (actually closer to 30 since i have about 100+lbs of sand and LR which will displace at least 3-4 gallons) X 5%=1.75 gallons of water i would have to change weekly. Ok, so take 1.75 or round up to 2gallons x 4 weeks (average weeks in a month)=8 gallons of water that is supposed to be changed per month (108 gallons of water a year--2gl/week*54weeks=108). I change about 20-30 gallons every month (at the current rate it would amount to be 270-405 gallons!!!! Hay dios mio!!:hmm3.

In effect, I am completely changing out the water in my system every month. Am I doing more "harm" to the tank by doing this? I have not seen any noticeable changes to the temperament of my fish and have seen my corals grow. However, not as fast as they should. Could this be the cause? All parameters are good except NO3 which usually hovers around .2-.75, NO2, NH3, PO4 are zero. I know and I am very aware that what works for me does not work for others and vice versa. I would like to get y'alls input on this matter cause I would like to go to the 5% water changes every week--RODI water is getting expensive!!!! So what is the "magical water change standard"? Thanks!

 

[strayvoltage]

I think you would be fine to do 5% a week that is 20% a month. Small weekly or biweekly water changes are better that one big water change a month. JMO

 

[jmait769]

I try to do 10% which would be about 10 gallons a month for mine! I do 5 gallon changes every other week. However because I have been a little neglectful lately due to the new tank I have not been so punctual. I have noticed a growth of zoas and other soft coral. When I did a water change recently I noticed that everything just looked better. I believe with a SPS dominate system more accurate water changes are a must. Not so sure on a softy tank now. Good article from Randy: Water Changes in Reef Aquaria

Jay

 

[willandmelsreef]

I dont know the standard but i do a 10 gallon change every 2 weeks on a 90 gallon with a 20 gallon sump. I have 150lbs of rock and 100 lbs of sand. So I figure its about a 10percent change bi weekly and 20 percent monthly and i've never had an issue with my water.

 

[Gomer]

I think it really depdends on a lot of factors. Bioload, tank size, skimmer efficiency (if one), macro refugium, and media used. With all these factors, I'd say between 5 to 20%. For well equiped tank larger, with fuges, good skimmers, and normal bioloads, you are floating on the 5% side. For something like a 14g biocube without a skimmer, you are looking around 20%.

In reefs, tank stability is more important. With that in mind, you are better off imo doing smaller weekly water changes then monthly. FOWLR are more forgiving, but inverts and coral dont take well to parameter swings.

 

[ryan_paskadi]

IMO small water changes are fairly useless at nutrient export. If you remove 10% of your water 10 times that does not remove 100% it removes approx~65%. If you do 5% water changes then it is even more inefficient. If you do four 25% water changes in the same length of time as the ten 10% water changes you remove approx~70% of that original water. If you do two 50% water changes you remove 75%.
It is impossible to remove all of that original 100% unless you do a 100% water change.
Your systems biological filter, protein skimmer, and refugium, act dynamically to increase or decrease nutrient export based on the nutrients in the water. Water changes do not do this. If you do small water changes very frequently the dynamic nutrient export adjusts to the average constant nutrients in the water. If you do no water changes those dynamic systems should just adjust to a higher level of nutrients.

IMO large very infrequent water changes are better at nutrient export. So why do small water changes work? I think it’s about what your adding not what your removing.

If you can effectively dose or add the equivalent nutrients you should not have to do any water changes.

 

[psuedopimp]

i can dig what ryan is saying. i always think of water changes as a breath of fresh air for the tank. i will change about 5 gal every month or two which is about 8% in my system.

 

[Gomer]

I agree, big water changes by definition work better as a nutrient export. There is a big trade off as I previously mentioned, and that is system shock. Reefs don't like change. Small water changes are much more forgiving with Alk/Mg/Ca/salinity/pH missmatches.

water changes are an export, but IMO, there are better options then big water changes. exports that are consistant are better for your system. These would include things like a maintained skimmer, a good macro base, and reactors for GFO/GAC on top of smaller, more periodic WCs.

YMMV.

 

[deehz]

I have a mixed reef. For a nano, I guess it is stocked pretty significantly--2 nems, 5 fish=15" long, LPS, sps, softies, and cleanup crew. Most would probably say that I am WAY over stocked. Every time I do a water change, I have to agree with the bigger water changes it is a "breath of fresh air" into the system. I do dose, only MG and a Kent all inclusive supplement 1 week after the water change 2x/week before the next water change.

It just seems a bit wasteful when I dump out all that water. I know that most of it evaporates. But I have to question really how wasteful the process is just to get rid of "bad" nutrients. I guess this is my biggest concern. I read on a thread from another forum that this guy does a 10% water change in his system every week. He has a 3000gallon reef!!!! that is 300gallons of water/week gone!!!! OUCH!! I thought the bigger the system, the more stable it is???

Most people, or diehard reefers, would say that he is doing the right thing and I am doing it wrong. The reefer "cops" would say NO NO NO, shame on you. Well, I guess in the other forum they would, this one has pretty cool, understanding people. But if you look at the responses, which I am greatfull for, you see that everyone does it a bit different. There is no consensus. There is no "true" guideline for this. Is this my understanding? Thanks!!

 

[psuedopimp]

there are really nice reefs that do water changes once a year, and really bad reefs that do water changes weekly and vice versa.

all about looking at your system and seeing what it needs. i don't think i would have the energy to change 300 gal a week. i don't think i do that in two years!!!

 

[psuedopimp]

if i remember correctly, don't you skim wet or something, and when you add top off you add alittle bit of salt also? isn't that a constant water change?

 

[deehz]

if i remember correctly, don't you skim wet or something, and when you add top off you add alittle bit of salt also? isn't that a constant water change?

Yes, I do skim wet.

And adding a lot of water due to evap for top off. At times I do add salt. I would think that this would be considered a "water change". Wouldn't it? The only difference is that I am not exporting bad nutrients. You see the predicament here Justin?

 

[psuedopimp]

but you are? when you skim wet that is taking it out. and that way you are never letting them build up needing a larger water change.

 

[strayvoltage]

Here is a good read on the subject.
http://reefkeeping.com/issues/2005-10/rhf/index.php