How big of a PWC is too big?

[Floyd R Turbo]

I'm assuming that as long as you match water conditions (salinity, pH, temp, KH) that you could theoretically do as large a percentage PWC as necessary, but is there a practical limit? Tank is a 125 with high Nitrates, so I need to get it down to a level where I can then pinpoint the problem/source (it's really high).

 

[CaptainAhab]

Personally I wouldn't go above 50%. If it's really that high then perhaps a large (50%), followed by successive smaller 20% until you reach your target level. I'm sure you know this, but it's only a band-aid. You need to address the cause. Nitrates is the effect.

 

[melosu58]

I would not do more than a 50% either. IMO you sometimes change the chemical makeup of the water if you change too much at one time.

 

[Floyd R Turbo]

Sounds good, since they have 125 DT and about 15 sump, effective 140g sytem water, I was going to do a large PWC of right around 50 gallons, or about 35% and then monitor the levels over a week to see how it balances out. Right now the Nitrates are over 100 ppm on my Salifert kit, and too high to really tell where it's at on API, the colors at that level just blend together. For anyone who was following my thread about starting up aquarium maintenance, it's the same system. The guy doing it now isn't addressing the issue, and the guy I thought could help them isn't doing anything consistently.

On top of that, I found another customer in a Chinese restaurant with a 125 long FOWLR, super dirty, no protein skimmer, not enough LR, no CUC, but has had no fish die in years. He's got 3 Sergeant Majors, a dog-faced puffer, and a yellow tang. One of the SMs has swollen gills to the point where it looks like something fleshy is hanging out of his gills at the bottom. Tried to get a pic to post but no luck. Nitrates off the scale on that one too.

He's also got a 225 that he had Discus in but they all died, and I'm going to set that one up as a cichlid tank with PFS substrate.

His Uncle used to take care of the tanks, and when he moved, they went downhill apparently. How the SW has even survived without a skimmer I have no idea.

 

[Floyd R Turbo]

I seem to be finding a lot of opinions on how frequently water changes should be performed. You talk to 4 people, and you get 6 opinions. I have read that on a reef system, you should plan on doing a 10% PWC weekly, or at least a 20% PWC every other week.

Someone today told me that in an established reef system of 125g, you could get away with doing one 20% PWC every month.

Doesn't that seem a little extreme? I mean, I do 30-40% every 7 to 10 days on my FW planted tank, granted it's packed full, but I would think I reef system would need at least 10% a week, unless it's lightly stocked and well taken care of. Am I wrong?

 

[thincat]

Floyd, which ever you decide, a 20% PWC is better then two 10% because you are removing much more DOC's with the 20% then with the two 10%.

 

[abrahamavelar]

are u using ro di water?????????? that might also help

 

[mdaniel2882]

Floyd, which ever you decide, a 20% PWC is better then two 10% because you are removing much more DOC's with the 20% then with the two 10%.

Not really. of the intial volume your are removing 20% with a 20% water change and 19% with 2 10% water changes.

 

[mfdrookie516]

Not really. of the intial volume your are removing 20% with a 20% water change and 19% with 2 10% water changes.

how does 10% X 2 = 19%?

 

[Floyd R Turbo]

how does 10% X 2 = 19%?

Example:

100 gallons

Change 10% (10 gallons)

result: 90 gallons original, 10 gallons new

Change 10 gallons again, you are changing 90% original and 10% new, or 9 gallons of original

10+9=19 gallons effective water change.

 

[Floyd R Turbo]

I will be using RO water to start, I don't have a DI unit - yet. But the Culligan filtered water at Wal-Mart is 37 cents/gal and is sediment, carbon, RO, and UV filtered, so for the immediate moment it's the best I can get. I have an whole-house RO system and another RO stand-alone to hook up for PWCs.

 

[Kurt_Nelson]

I seem to be finding a lot of opinions on how frequently water changes should be performed. You talk to 4 people, and you get 6 opinions.

I'm surprised you only got 6 different opinions!

Individual tanks have different requirements. What may work for one person - and be the basis for their opinion - may lead to disaster for another person. You just have to weigh all the different opinions, understand the "why" of what they're doing, and make your own opinion.

My opinion, based on my tank... weekly 10% changes, or 20% changes every other week.

 

[abrahamavelar]

you can always buy water from ur lfs mine sells it at about 20 cents per gal but i got a 6 stage ro di unit that i paid 95 bucks for on ebay

 

[tonedogz]

nitrates

Floyd, I had the same problem my nitrates were 140 for years couldn't get them down. Finally I spoke with a friend who told me to remove some of the sand in my tank. I did a 25% water change removed half my rock and vacuumed up all the debris that had been under the rock you quite some time along with some of the sand also rinsed the rock in salt water to get it clean of debris. Then two weeks later I did the same to the other half and now my nitrates are 20. Hope this will help.

 

[melosu58]

Read this

Water Changes in Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

 

[Floyd R Turbo]

Great article, thanks!!!

Yeah he has very little sand, maybe 1cm overall coverage, and that's after he added a bag last Monday. The other stuff was starting to look pretty dirty, but I'm not sure if he removed any of it. It looks pretty clean now.

I did 2 x 18g changes this weekend on 140g system water, or effectively about 23%. The sump was super nasty, when we took the pump off we both about choked, it smelled like a sewer.