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VitalApparatus
06/05/2011, 07:40 AM
What is the largest water change you could saftly do on a tank with 120 gallons of water volume?

Thanks

tspors
06/05/2011, 09:03 AM
The question for us to you is why and for what purpose?

VitalApparatus
06/05/2011, 09:04 AM
Nitrate reduction.My bio pellet reactor has only been running about a month and my nitrate levels haven't dropped any.

guarda
06/05/2011, 09:05 AM
I did very close to 100% to no ill effects.

papawheelie
06/05/2011, 09:06 AM
I would say no more that 50% without re-cycling

spieszak
06/05/2011, 09:08 AM
I don't really think the water volume is the problem... for all practical purposes you can do all of it... I don't ever go beyond where my rocks are exposed though, even though for the few minutes of exposure, there is probably very little that would happen. Personally, when I get into a scenario where I think I might want that large a water change though, I do multiple smaller ones over a week, so as not to shock my inhabitants as much.......and to keep things as stable as possible. Also, if I'm "battling" something, I like to see how it reacts to the change before moving forward.

VitalApparatus
06/05/2011, 09:09 AM
Ill do 30 percent today and go from there then.
Thanks all

papawheelie
06/05/2011, 09:09 AM
FWIW, I had nitrates steady @ about 30 until I added an ATS in my sump 2 weeks ago. Now they're @ about 10 and still dropping. Same thing with Phosphates, was at 1, now at .25, and the screen hasn't even fully matured yet.

tspors
06/05/2011, 09:16 AM
30% is cool, Nitrates under 30 is not bad at all.

steelhead77
06/05/2011, 09:17 AM
Last summer my nitrates were nearing the 100 mark. I did four 50% water changes (about 90 gallons each) in four weeks. Those effectively brought my nitrates down to near 0 where they have stayed since. Not a single negative issue was seen in any of my livestock.

VitalApparatus
06/05/2011, 11:28 AM
FWIW, I had nitrates steady @ about 30 until I added an ATS in my sump 2 weeks ago. Now they're @ about 10 and still dropping. Same thing with Phosphates, was at 1, now at .25, and the screen hasn't even fully matured yet.

Whats an ATS?

papawheelie
06/05/2011, 11:36 AM
Algae Turf Scrubber. Look in the advanced section, and there is more than you ever wanted to know about them. It should be on e of the first stickies under algae scrubber basics.

MrTuskfish
06/05/2011, 11:44 AM
I would say no more that 50% without re-cycling

Water changes won't have any effect on the tank's cycle. The friendly bacteria lives almost completely in the LR, substrate, etc----not the water column. If, temp PH and SG are almost identical, you can change as much as you want.

duncantse
06/05/2011, 11:45 AM
water changes won't have any effect on the tank's cycle. The friendly bacteria lives almost completely in the lr, substrate, etc----not the water column. If, temp ph and sg are almost identical, you can change as much as you want.

+1

lordofthereef
06/05/2011, 11:48 AM
The more you change (percentage of total), the more crucial it is you match all params (it's always important, but you can get away with murder with small percentage WCs). Sometimes we do changes to lower nutrients, but sudden (instant) removal of those nutrients can shock our inhabitants as well.

papawheelie
06/05/2011, 11:52 AM
Gotcha. Not what I have had recommended to me by two of the LFS's where I live. I just recently moved a tank and I was told to keep at least 50% of the water by two owners of shops that have been open for a long time. I personally would never change more than 50% of mine at one time.

aleonn
06/05/2011, 12:27 PM
The most I would do is 25% at a time so that water parameters don't fluctuate too much if I forget to match parameters exactly.

guarda
06/05/2011, 12:36 PM
I would normally never change more than 25% either but if you have a 1/2 lb of nutrafin pellets in your tank you are not going to wait a month to change out as much as you can. I believe the OP is talking about emergency measures.

insomniac2k2
06/05/2011, 03:29 PM
I had a high nitrate situation caused likely by die-off from a tank move. I did quite a few 75% water changes with very little results towards nitrate reduction. If you know or at least suspect your nitrate issue is being caused by "some" source (not just poor maintenance), i would say look into VSV dosing. I ended up using AZN03 with amazing results. 100ppm nitrates down to 0 in 2 weeks. Im now in the process of weening my tank off AZN03 and will then will go back to VSV.

Just one of my experiences with a product that worked well. YMMV