How often is best to make a "water change"?

[fablau]

Hi folks, I have been playing with my 75gl tank for years enjoying very nice plant grow and sometimes experiencing pain from algae blooming. So far I have been doing a 50% water change every 2 weeks, but I am thinking that maybe doing it once a week could improve the status of my plants even more and reduce algae that are always "around the corner" in my own experience.

What do you suggest? What's the best water change schedule for a planted tank? I couldn't find a specific answer on the forums, so I decided to post a specific question about it.

Here is my current setup and method:

75gl tank, pressurized Co2 (3-4 bps), 120w light 8 hr/day, complete Seachem line dosed as instructed every day, mixed population of tetras, other small fish and shrimps (about 50 fish, 60-100 shrimps), about 12 kind of plants pretty much all growing well (but I think some of them can improve and be completely algae free).

I am open to your advice!

Thanks.

Fab.


---
I am here: http://maps.google.com/maps?ll=33.522158,-117.698412

[Crispino Ramos]

What's your filtration and substrate?

[fablau]

Yeah, sorry, I forgot that: I have a sump with wet/dry filter. Substrate is Eco-Complete.

Thanks.

[Cyclesafe]

My automatic water change system replaces 2 gallons every 6 hours on my 120. This allows me to achieve a steady state of nutrients / pollutants that the plants and fish have adapted too. No algae and lots or breeding, respectively.

I think that changing water every week is better than twice as much every two weeks. How much better is difficult to gauge.

[fablau]

Wow, automatic water change is really cool! I begin to understand that would be probably better to change 30% weekly than 50% bi-monthly. I am willing to try that!

Thanks.

Fab.


---
I am here: http://maps.google.com/maps?ll=33.516119,-117.686979

[DukeNJ]

TFH magazine published an article comparing freq small vs less frequent large water changes a year or two ago.

It concluded that larger WCs were superior for water quality than more frequent small WCs because the smaller changes allowed greater overall buildup of undesirable stuff.

However, stability be an issue I'd your tank is significantly different from your tap water and volume may be a challenge if you need to modify your water before using it. So if your rank and your tap is compatible, adjust your temp close to tank and go for the big one.

[fablau]

This is interesting DukeNJ... any more thoughts from our expert gurus here?

Thanks.

Fab.