Doing super frequent water changes.. what can go wrong?

[jimbo222]

hmm maybe no need for a skimmer anymore mith that many water changes

[kien]

I did think about the cost and reasoned that the amount of salt that I would need would probably be near what larger systems, say, 280g and up would use on a regular basis anyway? Plus, if this did produce an ULNS then that would eliminate the need for additives, but it sounds like this wouldn't be the case

.. thinking out loud here.. I wonder what would happen if you did frequent enough water changes to the point where the water in the tank was (nearly) constantly equal to fresh saltwater. Like say 90% fresh saltwater all the time?

[bauder1986]

well your corals would grow nice and fast and the fish would be healthy thats for sure.

[Delphinus]

We might be getting into two separate topics though here: reefbuilding and nutrient management. Dosing is really more about managing parameters that are directly responsible for coral growth; nutrient export helps growth in that nutrient buildup will inhibit growth so removing nutrients (and by extension, ULNS) will remove those inhibiting factors. But even a zero nutrient system won't grow corals if there is no calcium or alkalinity or magnesium to begin with.

So. Water changes does benefit both goals by removing the baddies and replacing the goodies that get used up. Certainly there are tanks out there that use only water changes as the primary tool and these are nice setups. And indeed, do enough water changes and you might not really need a skimmer.

But what I think you'll find is that with water changes alone, you will only be able to go so far with it. In a low demand system, it may be enough forever. But in a high demand system (such as one with SPS), the draw on the calcium and alkalinity is not linear over time. Ie., as your corals grow bigger, so too does their apetites for calcium, and thus you have to add more Ca and Alk to compensate. At a point you will find, I think anyhow, that water changes alone won't cut it, and you have to manually replace Ca and Alk anyhow (either by dosing or by calcium reactor). The main thing about this is that the Ca and Alk is now decoupled from the nutrient export - which ultimately is a good thing because the rate of Ca and Alk usage likely isn't directly proportional to the nutrient buildup (which is going to depend on the fish load, and how much/how often you feed, etc.)

So, I'm not saying I think it's a "bad" idea, but I think it's just not the most efficient or cost-effective method out there.

[Delphinus]

This is the article I was thinking of, BTW:
http://reefkeeping.com/issues/2005-10/rhf/index.php

A quick glance at it now though tells me I might have given the wrong synopsis for the article. So ..um .. disregard anything I said about "less is more" until you've read the whole thing for yourself and come to the same conclusion and if you come to a different conclusion please let me know so I can stop misquoting it.

[Myka]

I have done this, and I haven't noticed much of a difference until you get up closer towards 25% twice a week. I think you're better off achieving ULNS with Zeo or even vodka dosing. Cheaper in the long I'm betting.

[sphelps]

While doing larger water changes less often is more efficient in lowering nutrients than smaller ones more often, stability is better with the smaller more often approach. This is why many people find better results with weekly changes over monthly ones. The question is, is there a line where too often becomes a problem? Is weekly really the most often you can go for best results? I don't personally think so, for a reef system I would promote more often as better, you'll just have to change a little more water each time to match the effectiveness of weekly or monthly changes.

I've setup a few systems including my own which use a similar principal but for different reasons. For automation or semi-automation smaller daily changes creates a simpler system and requires less water storage. Using this method I've always seen good results as stability is increased. Salt is either added manually or the top off water is has enough salt content to match the system requirements to maintain constant salinity. Using this method I've never noticed much change in skimming. I've also noticed my skimmer will stop working properly for about an hour after a standard 10% water change, so I don't see any real potential for a skimming problem.

As a final note I'll mention that public aquariums change water in their systems on a daily basis, I suspect they do this for two main reasons, 1 maintain low nutrients and good water quality and 2 maintain stability in reason 1.

Perhaps the loss in efficiency is outweighed by the gain in stability and simplicity. It makes much more sense to me to distribute a large water change into smaller ones, how often depends on how much water needs to be changed.

[sphelps]

Originally Posted by Myka

I think you're better off achieving ULNS with Zeo or even vodka dosing. Cheaper in the long I'm betting.

Running a basic zeo system on a 100gallon tank runs for about $60/month, depending on your salt brand, that same amount of money would pay for around 100 gallons of water each month. That's 10 10% water changes or roughly 2.5 10% changes per week. Sounds about the same until you consider zeo tanks require weekly 10% water changes, then it's obvious zeo tanks cost more.

[Delphinus]

Sorry Steve, I missed that you were only talking of nutrients. Somewhere on the first page Kien mentioned in passing that (to paraphrase a bit because I'm too lazy to go find it and quote it) that it would be nice if this could also eliminate the need for additives. Which I took to mean the big 3 (Ca/Alk/Mg). I wasn't sure if you were addressing that, or the nutrient thing. So I guess I'm in total agreement with ya, you were just better with the graphs and math and stuff.

[kien]

Thanks for all the input everyone. Some great information here!

To clarify, when I said I wanted to eliminate the use of additives I meant additive designed to reduce unwanted nutrients like Zeo,Fauna,Vodka,Gfo, carbon etc.. There is a lot of stuff out there And I was just wondering if there was a way to simplify nutrient export to achieve a near ULNS. That's when the frequent water change came to mind.

It sounds like some have tried this without it making much of a difference though. Yes, cost would be higher but then people with larger systems need to spend this type of coin on their "regular" water changes.

Aside from possibly nuking my beneficial bacteria it sounds like there isn't much that can go wrong here. As mentioned, I think stability is the key. Lots of small-medium water changes. I may try this out for a few months and see how it goes. I suspect in the end I will get sick and tired of all the water changes but I'm still curious to see the results.