many small water changes vs. one large one, rocks toppling over, ect..

[holdyourlight]

My issue is as follows:
i just set up a 120g, i stacked the rock up all the way to the top of the water line in pillars. Some of it is held together by rods but most is just held together by gravity. I need to do a large water change and am pretty certain that when i drain the tank half way that the rocks are going to topple over since gravity in air is different than water. my sump only holds about 15 gallons and i could just vacuum that out. so if i can't change out 60 gallons in one shot should i just do a bunch of small water changes? what are your thoughts?
thanks

[maymania6]

My first thoughts would be to secure your rock work. You'd hate to lose a fish or coral due to a fall. Next thought is why do you need to do a 40% + water change? Problems? If your parameters are stable I'd think that doing small, more frequent water changes via the sump would be sufficient.

[Curious George]

I agree, I think the first order of business is to secure the rock. If it is a reef tank with corals/inverts, I would do smaller water changes---like 15% every other week. If it is a fish only tank, I opt for 30% once a month.

I read an article in TFH where they broke down water changes and concluded that one large change was better than many smaller throughout the month. The reason being that you are removing more bad water and replacing clean with one large change.

[James77]

Yeah, I would secure your rockwork better.

Here is an article on water changes:
http://reefkeeping.com/issues/2005-10/rhf/index.php
To sum it up, many small water changes are almost equal to one large one.
In the case of small batch ones:

30 changes of 1% each exactly matches one 26% batch water change

In the case of continuous WC:
A continuous water change of 30% exactly matches one batch 26% water change.

[dublo8]

I agree, I think the first order of business is to secure the rock. If it is a reef tank with corals/inverts, I would do smaller water changes---like 15% every other week. If it is a fish only tank, I opt for 30% once a month.

I read an article in TFH where they broke down water changes and concluded that one large change was better than many smaller throughout the month. The reason being that you are removing more bad water and replacing clean with one large change.

Randy has an article stating that the difference between one large vs multiple small is indistinguishable.

But yes I would secure your rock work ASAP. Maybe use some underwater epoxy. Like mentioned before you don't want a landslide. Plus if they are stacked that high you risk having them fall against the glass and causing bigger issues.


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[albano]

am pretty certain that when i drain the tank half way that the rocks are going to topple over since gravity in air is different than water.
I'm not so sure about that...with the current from a powerhead, the rocks have more than just gravity 'fighting' their stability!


Secure the rorks!

[holdyourlight]

OK guys maybe i wasn't so clear on the rocks. There is no chance of them falling over while they are underwater, they have been fine for a couple months so far and i have kids running and jumping right next to the tank all of the time. I am just worried that once i drain a whole bunch of water that they will topple over since gravity is different in air and water. the reason i am performing a huge water change is that the tank has just finished cycling, nitrates are sky high and i need to get them down

[albano]

There is no chance of them falling over while they are underwater,
FAMOUS LAST WORDS!....my Dad always said, "show me a guy that says 'no problem', and I'll show you a problem!"

If they can fall over out of water, they can fall over in water...despite your experiences on other planets. :eek1:

[sporto0]

A 50% water change is a good idea considering the tank has just finished cycling. I don't know how you have any peace of mind with your rock work if you think there is any chance it might fall & scratch the glass at least & possibly crack the tank at worst. I know that I would not trust that scenario. Good luck to you.

[holdyourlight]

FAMOUS LAST WORDS!....my Dad always said, "show me a guy that says 'no problem', and I'll show you a problem!"

If they can fall over out of water, they can fall over in water...despite you experiences on other planets. :eek1:

A 50% water change is a good idea considering the tank has just finished cycling. I don't know how you have any peace of mind with your rock work if you think there is any chance it might fall & scratch the glass at least & possibly crack the tank at worst. I know that I would not trust that scenario. Good luck to you.

thanks for the advice guys.
this is the aquascape i based it off of. his are all tied together with rods.
mine are for the most part except a few of them.
in past tanks over the last 5 years i never even used rods. i would expect that the majority of people still just stack their rocks.
obviously you would need rods or something if it is going to be as tall and narrow as in the picture