Large water change VS. several small ones!?

[Azteky]

Our tank is 5+ years old and the Phosphate is getting high, never did a water change before so wondering to get my tank back in shape, would it be better to do several small water changes every other day (maybe 5-10 gallons a day?), or one large change? (50% or so?) Its a 72 Gallon with around 250lbs of rock and a 4-6" DSB.

Thanks for any advice! =)

 

[username in use]

I would do multiple 50-75% water changes spaced 3-5 days apart. Then get on a schedule. If you can't commit to weekly 10%, then shoot for monthly 15-25% changes.

 

[Lilbitreefer]

the 50-75% water change seems a little high, I would be worried about causing a new cycle. I have read around that 5 20% water changes every 3 days is basically doing a 100% water change with out throwing the bacteria balance off to much or stressing the fish out too much. but I'm still new at this.

 

[username in use]

I've done 100% water changes in a pinch and everything was fine. The bacteria is in the rocks and sand, not the water so you aren't removing anything. As long as it doesn't take you eight hours to refill there shouldn't be any die off.

 

[klwheat]

Agree with above. Changing a large quantity of water makes little impact on bacteria as so little is actually in the water column itself. The vast majority of bacteria resides in the rock, sand, filter media, etc.
How high are your phosphates currently? What is your phosphate goal?

 

[Azteky]

Phosphates are 1.27.... yup, I know, very high! Our tank is still growing stuff like mad but the last few weeks we have certain Zoa's that are not opening anymore. So is there any pro's / con's to large changes or smaller ones? or does it not make a difference, I would think larger would take away more of the crap in the water as several smaller ones would be taking away the fresh water too!?

 

[kozmic]

Temp/Ph/Salinity are prob your biggest risks with large changes... I personally, would try to be sure those are all even with your current water, then do about 25% every other day for a week or so, then re-test... if still high, rinse/repeat...

But that's just one man's opinion, and like just about everything else in this hobby, there's good arguments for just about everything... :thumbsup:

 

[Chibils]

the 50-75% water change seems a little high, I would be worried about causing a new cycle. I have read around that 5 20% water changes every 3 days is basically doing a 100% water change with out throwing the bacteria balance off to much or stressing the fish out too much. but I'm still new at this.

5 x 20% adds up to 100%, but by the second water change only 80% of the "original gross water" is left so a 20% WC removes 16% of the "original gross water". By the third water change you're only removing 12.8% of it, then 10.24%... By the time you've done 5 x 20% water changss, only 67% of the water you started with has been removed instead of 100%.

Hope that's not too confusing.

 

[CStrickland]

Phosphates are 1.27.... I would think larger would take away more of the crap in the water as several smaller ones would be taking away the fresh water too!?

yup, but the upside of smaller changes is you dont have to be as careful in matching temp/salinity/alk/ph. I can do a 10% change without even heating up the water and nobody notices. More that 15-20% and that would be dangerous. A few degrees of temp diff can kill fish, or if you have ich in your tank that is not symptomatic that kind of stress can lead to an outbreak.

Some bad news about phosphates though, is they can be absorbed by your rocks and sand. It's very likely that even if you changed all the water, more phos would leach into the new water fairly quickly. That can take a few months to resolve, but there are a few shortcuts you can use. You might want to read some threads about "dosing lanthanum chloride" and see if that appeals to you. Or crank up a GFO reactor.

 

[Skim]

I would hold on the large changes. You say you did no water changes in 5 years, if thats is true then I would do small amounts of changes as anything you do will be a shock to the tank and usually shocks are not good things.

 

[Azteky]

So what percent should I be doing, 10-20% every other day? I don't want to screw anything up.. So far I have been doing 4 gallons a day (Again its a 72 gallon) I got my salinity down to 1.026 so that's ok, haven't tested Phos since Sunday but will do that tonight and see what its at. I also have a GFO that I will throw in there.

 

[xkon]

I feel like a 72g with a DSB and 250lbs or rock would be so crammed you would have only like 30g of water in there lol

 

[slief]

So what percent should I be doing, 10-20% every other day? I don't want to screw anything up.. So far I have been doing 4 gallons a day (Again its a 72 gallon) I got my salinity down to 1.026 so that's ok, haven't tested Phos since Sunday but will do that tonight and see what its at. I also have a GFO that I will throw in there.

I am a firm believer that smaller daily water changes are much easer on the tanks inhabitants than larger ones. As mentioned above, you don't need to match temp or parameters like you do with larger water changes and it's less shock to the system. Also, with smaller daily water changes, the system is consistently cleaner than it is doing larger weekly or bi-weekly changes because waste and nutrients don't really have a chance to build up like they do with less frequent water changes. The end result is a healthier system with less need for as great of volume in water changes per month.

I have a 480 gallon display with 650 gallon over all volume. I have 50+ fish of which several are over 8". There is well over 130 inches (combined length) of fish in my system (probably closer to 160" of fish) not including girth which is a fairly heavy load. I change out 5 gallons a day for a total of 150 gallons a month. That's about 23% monthly in water changes and I never have detectable nitrates despite 3 feedings a day. The last of which is a huge feeding. I also don't carbon dose or run bio pellets or anything like that. To top it all off, I don't have nuisance algae issues and I never do large water changes.

The more frequently you change water, the less overall water needs to be changed in my experience. Especially in a well thought out system with sufficient biological surfaces. That said, every tank is different so determining how much really needs to be changed is purely speculative. It all depends on your parameters and the health of your system.

 

[Skim]

I am a firm believer that smaller daily water changes are much easer on the tanks inhabitants than larger ones. As mentioned above, you don't need to match temp or parameters like you do with larger water changes and it's less shock to the system. Also, with smaller daily water changes, the system is consistently cleaner than it is doing larger weekly or bi-weekly changes because waste and nutrients don't really have a chance to build up like they do with less frequent water changes. The end result is a healthier system with less need for as great of volume in water changes per month.

I have a 480 gallon display with 650 gallon over all volume. I have 50+ fish of which several are over 8". There is well over 130 inches (combined length) of fish in my system (probably closer to 160" of fish) not including girth which is a fairly heavy load. I change out 5 gallons a day for a total of 150 gallons a month. That's about 23% monthly in water changes and I never have detectable nitrates despite 3 feedings a day. The last of which is a huge feeding. I also don't carbon dose or run bio pellets or anything like that. To top it all off, I don't have nuisance algae issues and I never do large water changes.

The more frequently you change water, the less overall water needs to be changed in my experience. Especially in a well thought out system with sufficient biological surfaces. That said, every tank is different so determining how much really needs to be changed is purely speculative. It all depends on your parameters and the health of your system.

Great advice! If everyday is too much for you to fit in try doing for 1 week and then try twice a week and then drop it to once a week when things level off and see if that will do it for you. Basicly try to fit something that will be good for the tank and yourself so keep an eye on the PO4 and NO3 and work around those.

Good luck!

Skim

 

[PIPSTER]

If the only reason for the water change is to reduce PO4, I'd look at some other way to reduce it.

Otherwise, the largest water change at one time that you're comfortable with will remove the most "contaminants".

But there's lots of people who have done large water changes and not seen their PO4 levels go down at all because it's leaching just as fast out of rocks and sand.

Have you looked at algae scrubbers?

 

[Sounds Fishy]

I have been doing a 5 gallon water change daily for a year now.It is routine and only takes 5 minutes.I think it keeps trace elements at an acceptable level,and is a good nitrate export.