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

[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.

[Red Coral Aquariums]

Originally Posted by kien

.. 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?

I would be nervous about losing your beneficial bacteria causing a mini cycle. I've seen a tank crash from 3 times 60% water changes and each one was done daily. 4 th day before h2o change ammonia reading was 3. This person wanted to bring down his nitrates from 20 to 5. He saved his tank by doing 10% daily water changes for a week. Subsequently after that week his nitrates were 7.

Kevin

[wickedfrags]

Generally agree with Tony's thought on p1.

The cost of the salt would outweigh the likely benefits. Perhaps consider less fish or feeding them only 2x's a week. Afterall, you don't need to remove what you do not put in. Maybe go with less water changes and less feeding for a while and see how it goes, was my approach back in 2006/2007.

[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.

[sphelps]

Originally Posted by wickedfrags.com

The cost of the salt would outweigh the likely benefits. Perhaps consider less fish or feeding them only 2x's a week. Afterall, you don't need to remove what you do not put in. Maybe go with less water changes and less feeding for a while and see how it goes, was my approach back in 2006/2007.

While I agree with this logic I don't think it directly applies here. While larger water changes are definitely more effective in lowering nutrients, I don't believe the same is true for maintaining nutrients at a certain level. This is something I made up a while back to aid in explaining effects of water changes and also why so many people have nutrient problems.

The example is simple and as follows. A system containing 100ppm or nutrients at week one. The system on average adds 5ppm of nutrients each month or 1.25ppm each week. The chart shows how the nutrients decrease when comparing 25% monthly changes to 6.25% weekly changes (same amount of water assuming 4 weeks per month).



It's obvious that monthly changes decrease the level sooner but once it reaches a critical level it remains constant and both monthly and weekly changes become equal. Also notice that the nutrients will never return to zero (why many people always fight nitrate levels) and that the weekly changes produce a more stable level.

So for maintaining low nutrients smaller more often changes may be better while for lowering nutrients larger changes less often are more effective.

I'll also say that while the obvious solution is to cut off the source as already stated this still has limits. Experts and authors will insist that fish require several feedings daily, this of course is not piratical for most reef keepers and we develop different approaches. I for one feed once daily and skip a day once in a while. However feeding less can result in some fish not being able to compete and starving to death. Feeding even less can result in all fish not being able to keep the required nutrients which can eventually cause death as well. One could cut the source even further back and decrease the amount of fish but with this logic why not remove the tank all together and eliminate the problem completely? While this may seem harsh I think if someone is willing to spend more on water changes to keep a couple more fish or feed a little more, that's his or her option.

[Delphinus]

Steve, I completely agree that "smaller, more often" produces a more stable system, and this is better; but doesn't a reactor or dosing routine offer higher control of the parameters? ... Hmmm, I guess if you're not as concerned with where they are, just that they are "good enough" then I guess it doesn't matter as much. The only thing is, you need to make sure your incoming water has good parameters and it's a rare salt that offers consistency in numbers year after year: you'll end up dosing into your makeup water anyhow, and at that point does it really matter if you dose your incoming water or your tank?

[sphelps]

Originally Posted by Delphinus

Steve, I completely agree that "smaller, more often" produces a more stable system, and this is better; but doesn't a reactor or dosing routine offer higher control of the parameters? ... Hmmm, I guess if you're not as concerned with where they are, just that they are "good enough" then I guess it doesn't matter as much. The only thing is, you need to make sure your incoming water has good parameters and it's a rare salt that offers consistency in numbers year after year: you'll end up dosing into your makeup water anyhow, and at that point does it really matter if you dose your incoming water or your tank?

Just to be clear are you talking about levels of elements such as alk and Ca? And by reactor are talking about a Ca reactor as an example? My previous discussion was based on the assumption that these levels are out of the scope of this particular discussion as it seems to be more based on removing unwanted nutrients from the system, not replenishing elements. However I don't think the idea behind more frequent water changes is to eliminate the need for dosing or using such reactors, these may still be needed just as if only monthly water changes were preformed. If this were the case I would still assume more stable levels all around using the smaller more often approach, dosing or whatever would be easier to tune for consistent and smaller changes that occur more often than compared to a single larger change which occurred less often like a monthly basis. Inconsistent salt will effect both methods equally and therefore I don't think it's a variable of great concern in this discussion.

Dosing or other means of replenishing elements also may not be required if significant water is replaced often, however that will depend on many things.

[sphelps]

Another interesting theory to consider is: No matter how much water you change it's not enough to maintain ultra low nutrients. Something else, like a skimmer for example, is always needed.

Even if a tank starts at 0ppm nutrients, and only adds 0.5ppm a week and you change 25% of water weekly you'll still build up to a stable level of 2ppm. This may not seem like a lot but keep in mind it's just an example to show the theory. You will never maintain 0 nutrients with water changes alone.