Question about water changes....how much..how often...etc

[Cancun]

Hi all! What is the BEST rule of thumb for how often and how much to do water changes? I have a 29 gallon biocube....nitrites are 0....ammonia is 0....but nitrates fluctuate between 10 and 40 ppm....started out doing monthly 20% wc...then 10% every other week. ...now 10% every week to lower nitrates. ..but read articles that it may not be good for yhe tank to do so much water at once?? Any advice or info would be great!

[shovelnose]

Smaller frequent water changes are best so you don't change your water parameters to rapidly. Unless you have a major tank melt down. 10% per week should work for you. Not an expert but just my opinion. I change 10% every 2 weeks. So far so good.

[dmh8801]

I do 20-25% once a month.

[gone fishin]

IMO it depends on your stocking and equipment. I would think 10%/week would be a good start.

[johnike]

15% every three weeks or so here.

[stlcards14]

If you're doing a reef tank do 10% a week to replenish trace elements

[igot2gats]

Smaller frequent water changes are best so you don't change your water parameters to rapidly.

This ^

Not only will it keep your params from not swinging a ton, but it gets you to check & look at your tank on a scheduled basis.

[thegrun]

For smaller tanks like yours I've found weekly 10% water changes are best (as opposed to 15% every other week).

[dkeller_nc]

One thing you'll realize from a quick calculation is that a water change is a lousy way to manage nutrients that get generated by the animals. At least a water change in the 10-20% range. Even if nitrate didn't get generated by the tank inhabitants, getting 40 ppm of nitrate down to the sub 5ppm range would require 20 successive 10% changes.

So water changes are a good way to ensure that the balance of ions in the tank water doesn't get too far away natural seawater ratios, not so good to ensure water quality.

To control nitrate and phosphate, it's a lot better to employ chemical & biological means of control. In the case of nitrate control, carbon dosing has been a real revolution in saltwater aquarium keeping. In the case of phosphate management, export of bacteria via an efficient skimmer helps, as does direct chemical filtration with granular ferric oxide (GFO).

[Spyderturbo007]

I was doing 20% every other week until I started plotting my parameters. Once I did that, I noticed a spike after each water change. I have since switched to 10% every week and don't have that spike.