Water Change Frequency

[d2mini]

Hi, I've been wondering if there is any data on the effects of multiple smaller water changes vs single large water changes. I think it's pretty widely accepted that the smaller more frequent changes mimic the ocean more closely and create less stress on the inhabitants due to greater stability of temp, trace elements, etc. But my reason for asking has more to do with the percentage of water changed. Would it be safe to say that doing one single 10% water change once a week would be the same as dividing that up by the number of smaller water changes and using that figure to program your dosing pumps?

In other words, lets look at 3 different water change scenarios on the same tank, keeping the weekly total amount the same.

#1 - Bucket, hose and changing out 10% all at one time, once per week. Roughly 15 gallons.

#2 - Using a dosing system to perform 150 small water changes every day. Just a few ounces changed out each time, but if multiplied by 150x per day and then 7x per week, this number would equal the same 10% or 15 gallons total per week.

#3 - Using a dosing system to run just 6 times per day for about an hour each time. A much larger quantity is changed out each time compared to option #2. But multiplying by 6 per day and then 7 per week, ends up with the same 15 gallons per week.

The main reasons we perform water changes (correct me if I'm wrong) is to get rid of depleted dirty water and replace it with clean water and replenish trace elements. So if we were to decide that 10% per week when doing single water changes was the holy grail amount, would that number need to change at all when doing multiple smaller water changes throughout the week?

Would love to know if any research has been done on this or any thoughts any of you might have.

 

[rbirling]

Here's a great article on the subject:
http://reefkeeping.com/issues/2005-10/rhf/index.php

 

[d2mini]

Thanks for the link!
What I was thinking (and what made me start this thread) is that the smaller, more frequent changes may require slightly more total water volume to be changed out to match the same benefits. Looks like I was on to something.

 

[rbirling]

Yeah, you're correct. The interesting thing is that it's not as much as you expect! This inspired me to do continuous changes on my system. The plus side is that you don't have to match all the parameters exactly since you're changing such a small amount at a time. For example, I don't heat my replacement water.

 

[d2mini]

Ya, i've been doing it for a while now with a LiterMeterIII setup and loved it.
Now switching over to my Profilux system using their doser and level sensors. In the middle of setting that up and wondering if I should be making any adjustment to quantity one way or the other.

Good to know that it doesn't need much adjustment.

How much total volume do you change out over the course of a week? On my old tank I was doing about 10% and was figuring on doing the same for my new build.

 

[rbirling]

I don't measure mine closely right now, but I'm shooting for about 1%/day in my head.

 

[psykobowler]

For me it is no longer about frequency and quantity of water changes but rather a technique. You could replace hundreds of gallons of water in any system but if you leave all the detritus and mulm in the tank it would be inefficient at best. You are only diluting the mulm and not removing it efficiently. I no longer maintain a weekly regiment of water changes. I just look in my sump for the build up of mulm and when I see a layer of mulm I siphon it out and replace the water taken out by the siphon with new saltwater (reef crystals). In addition, I also clean my refugium by shaking the chaeto to dislodge all mulm build up and siphoning this water out and replacing with new saltwater. In a 700+ gallon system I only water change 30 gallons to remove the detritus build up. My other technique is the modified wet skimming water changes with carbon dosing. When I see shades of hazy algae starting to build up on the acrylic display I perform the wet skimming water change technique. First I clean the skimmer neck thoroughly. I measure the sg. If it is 1.025 I add about 10 gallons of newly made saltwater. If it is 1.026 I add 10 gallons of ro/di water. This 10 gallons temporarily raises my sump level an inch and my skimmer starts to skim really wet to the point of slowly overflowing the cup. My skimmer cup has a drain that empties directly outside my house. I do this at night and by the time I wake up in the morning the water is clearer and the sump level returns to normal. I also use approx 10 ml of vodka. My skimmer ends up skimming bacteria which lowers nitrates, etc. I also harvest my chaeto every 2 weeks. This technique works so efficient for me that I only use a box of reef crystals per month and 2 cups of gfo. Whereas before I go through 2 boxes a month. Working on your nutrient export technique is more important than the amount and frequency of water changes. It's all about nutrient export and there are alternatives to just large and frequent water changes. Harvesting chaeto and dosing carbon goes a long way. Check out the wet skimming water changes thread. It really does work and saves on salt.

 

[d2mini]

Very interesting!
Thanks for the post!

Do you have any thoughts on the information you posted along with a tank that doesn't grow chaeto very well? I've had several tanks and my chaeto tends to survive, but not grow much at all. I usually have a pretty light fish bio-load and feed lightly, so I always assumed I just don't have the nutrients. Although I do get the nasty settling on the bottom of the sump. I guess I'm wondering if you would make changes to your "water change" ritual or anything else in your tank if your chaeto stopped growing.

 

[psykobowler]

I dose iron in my tank to help the chaeto. Research Fergon here in RC. Chaeto that slow down on growth but not die is a good sign.

 

[Ron Reefman]

I dose iron in my tank to help the chaeto. Research Fergon here in RC. Chaeto that slow down on growth but not die is a good sign.

I agree. That is just my situation. I have about a soccer ball size head of chaeto in my 2' x 2' x 16" fuge and it stopped growing about a year ago. I have some red macro algae in an attached anemone tank and it stopped growing soon after the chaeto. I have had zero nitrates about 3-4 months longer than zero growth macro algae. I don't even test for phospate as I have no algae growth. I don't run GFO or carbon, but I do have a diy nitrate reactor. I started dosing Fergon about 2 months ago and I still haven't seen any growth in the macro algae.

 

[tj1627]

A good tool that I've toyed around with to settle on a water change schedule:

http://www.theaquatools.com/water-changes-calculator

You can put in a few different scenarios and get an idea of where you'll be 3 months from now on small vs large changes

 

[avaross09]

Hey thanks for sharing this link, before I did not know about this water change calculator system.

 

[tj1627]

Hey thanks for sharing this link, before I did not know about this water change calculator system.

No problem. Anyone can sit down and do dilution calculations, but when figuring out a WC schedule, it helps to "tweak" it here and there to figure out how long it will take you to bring down high levels, if you'll slowly buildup because your changes aren't large/frequent enough, etc.

 

[Psyops]

About 6 months ago I started 1% daily water changes with the LitermeterIII system. I did not see much change or benefits. Then I started doing 2% daily water changes. That's when I saw the big difference. My corals started coloring up better than ever. I barely get any skimmate with my protein skimmers (yes two skimmers). I thought one of my skimmers was not working so I used my older one. They both get very little skimmate. My coral growth is exponential. I see differences in coral growth in a couple of days one some of the SPS. I don't know about long term use. I have added conches and a better CUC for deal with the detritus issues. Hope this helps guys.

Alex

 

[swcc]

I don't change water except to pull detritus as well. Really have no need... If ya just scoop out water and replace that seems like a waste of time over putting a siphon to use and removing pollutants from the tank.

OH, y'all should be proud cheato(or other macro) does not grow in your system...your probably running a nice ULN system. remove it...it is not needed for any reason. Don't forget that macro algae is added bio load...it may uptake one nutrient...but it also releases others.