Why should you do water changes?

[Psirex]

I think it mostly have to doe with Bio-load and feeding which increase nitrate levels and Phos levels.

 

[Randy Holmes-Farley]

Can you explain any more about the "maintenance of various elemental ratios like chloride/sufate." for this is the first I've heard anything about this issue?

And is activated carbon able to remove most kinds of dissolved organic carbon?

Chloride (Cl-) and sulfate (SO4--) are the two main negatively charged ions in seawater:

What is seawater
http://reefkeeping.com/issues/2005-11/rhf/index.php

from it:

Figure 3. Relative concentration of ions in seawater by weight.

The total of those two will be well controlled by the salinity, but the relative amounts of each can be skewed from natural ratios by additives such as calcium chloride or magnesium sulfate. Water changes will tend to bring them back to the ratio present in the salt mix.

I show that here:

Water Changes in Reef Aquaria
http://reefkeeping.com/issues/2005-10/rhf/index.php

from it:

Figure 25. Sulfate concentration as a function of time when performing daily water changes equivalent to 0% (no changes), 7.5%, 15% and 30% of the total volume each month (in other words, 0%, 0.25%, 0.5% and 1% per day). In this example, sulfate starts at a natural level of 2710 ppm, and the model assumes usage of a moderate amount of calcium chloride and sodium bicarbonate to maintain calcium and alkalinity, and Epsom salts (magnesium sulfate) to maintain magnesium.

 

[Randy Holmes-Farley]

And is activated carbon able to remove most kinds of dissolved organic carbon?

Many types, but not all. GAC won't do much for entirely hydrophilic organics.

 

[megatron8121]

12 gallons in my 100, 5 in my 29, and 1 in the 5 gallon weekly here. Numbers stay at 0 so I keep doing it.

 

[tmz]

Thanks Randy, I've been off line so didn't have a chance to answer and would have probably cited your articles or information learned from them in any case.

 

[sneaton]

i have a 75 gallon sps/lps tank that i run pellets on so my trates and phos are always in check...also i have brs dosing pumps to keep cal and alk in check and stable...so all i need to do replace trace elements.....do you think a 5 gallon weekly water change on 75 gallons is good, or do i need to do a 10 gallon change? please advise:spin3:

 

[BossHoggin]

i have a 75 gallon sps/lps tank that i run pellets on so my trates and phos are always in check...also i have brs dosing pumps to keep cal and alk in check and stable...so all i need to do replace trace elements.....do you think a 5 gallon weekly water change on 75 gallons is good, or do i need to do a 10 gallon change? please advise:spin3:

Depending on how much coral there is I dont see an issue. Testing your magnesium will be a good indicator of if the tank burns through more elements than you are replenishing with the 5G WC's

 

[sneaton]

Depending on how much coral there is I dont see an issue. Testing your magnesium will be a good indicator of if the tank burns through more elements than you are replenishing with the 5G WC's

nice...ive never added mag in 1.5 years in this tank until last month and that was just to bump it from 1300 to 1400....so i should be good if that is really a good way to judge....the tank is in my avatar so its getting more full as things grow in

 

[tmz]

Gerneral practice is to test for alkalinity more frequently than calcium or magnesium. Magnesium depletes slowly,usually monthly checks are more than adequate for it; alkalinity can drop quickly.
Water changes for my system total about 40% per month ie (1% per day plus another 10% or so related to maintenance),26.6 % or 20 gallons per month on a 75 @ 5 gallons per week is reasonable. I'd probably do 6 or 7 gallons per week.

 

[FizzOut]

This is an interesting thread about water changes. From what I can glean, water change is more important for putting back depleted chemicals into the tank rather than the removing unwanted chemicals in the tank.

Also, I don't know why 1% daily water change is considered the same as 30% per month water change, unless it is for the purpose of putting in depleted chemicals.

 

[Touring]

Iv had awesome results with Sea lab #28. Since I'm always deployed the only thing I tell my with to basically do is to put a block in when the other dissolves,empty the skim from the skimmer and when ever she feels like it change the filter floss.

Everything in my tank is awesome and growing. I have about 20 corals, mostly sps, scolly ,3 anemones and 2 clowns and a yellow tail. All growing super fast and awesome colors. Oh yea and its a 30 gallon. With no water changes....