Frequency of water change
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Old 11-06-2013, 06:01 PM   #1
randerson
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Frequency of water change


I'm sure this has been covered somewhere in the forum, but can't seem to find a thread.

How frequently is a water change needed with a high tech tank? Is it needed at all?

I'm noticing that my parameters are pretty good at the end of the week and don't really call for a water change. Nitrate levels are naturally staying low. Are we worried about trace nutrients or toxins building in the tank? Looking for sound science on this. I guess I'm asking, what's the point of doing a water change if all the parameters are good?
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Old 11-06-2013, 06:12 PM   #2
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Read up on the ei dosing method. I'd be wary of running a "high tech" tank with low nitrates. Typical ei dosing schedule calls for a 50% weekly waterchange.
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Old 11-06-2013, 06:23 PM   #3
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There are several schools of thought on this, and it is not a simple problem.

1) Fish only tank, no plants.
Fish food is the source of nitrogen, and there is no removal system other than water changes. There are associated things going on with the decomposing fish food, fish poop and the fish hormones, perhaps other things make water changes mandatory. The range of opinions seems to be that the NO3 should be kept under 20 ppm for optimum fish health. Some people insist that NO3 is not toxic, and can be really high. I do not know if NO3 itself is toxic, or perhaps it has to do with all the other things going on in the tank.
When I ran fish-only tanks I had them quite heavily stocked and had to do 50% weekly water changes to keep the NO3 under 20 ppm. If the NO3 started creeping up the fish became lethargic, and some diseases broke out. Mostly Columnaris.

2) Plants act to remove a LOT of toxins from the water. Maybe it is the plants themselves, or maybe it is a somewhat different group of microorganisms that thrive in a planted tank. I dunno. But a planted tank seems not to need as large water changes as a fish only tank.

3) If you are following the Estimative Index method of fertilizer then weekly 50% water changes are the way to start out. As you get to know your tank you can fine tune the fertilizer dosing and get by with smaller water changes.

4) No water changes will eventually deplete the carbonates in the tank. Some of the microorganisms use them as a source of carbon. When the KH drops, the pH drops. When the pH drops the microorganism population changes. This can make the tank toxic, but so slowly that the fish in the tank adapt, and survive. But new fish added are not so adapted, so they die. This is called Old Tank Syndrome and is basically a tank with not enough (frequency or volume) water changes.

So...

How often:
I prefer to suggest you follow a schedule of perhaps weekly water changes. That way, you have a chance to get into the tank and correct things before they get worse. Clean the filter, vacuum the largest debris, trim the plants... a little this time, something else next time... so that the total maintenance is not done all at once, but spread out.
How much: As a place to start, use the NO3 test. Keep the NO3 under 20 ppm. If it has climbed to 40 ppm, then you will need to do 50% today, and perhaps another 50% tomorrow. If the NO3 is right at 20, then maybe need 50%, but maybe less is OK. Monitor it and see how fast it comes back.
If you have to add fertilizer to keep the NO3 stable for the plants, then try 25% weekly water changes. This will generate enough water to clean the filter.
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Old 11-06-2013, 06:37 PM   #4
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Interesting. I was under the impression with ADA aquasoil, fertilization was not all that necessary. Looks like I have to invest in some good test kits for those nutrients and see what's going on. I'll also have to figure out if my plants are getting their nutrients primarily through the root system or the leaf structures.

I like the idea of doing a water change to do maintenance on the tank. It's a lot easier to clean inside with some of the water gone. Also coming from a previously gigantic tank, I would often spot problems I wouldn't have otherwise during a water change.

As for dKH I'm using a trick I found in my saltwater days, putting a bag of crushed oysters in the filter to maintain it. I had to take it out this week because the dKH got too high.

So the question is, is fertilizing necessary? They seem to be growing fine, pearling and all.
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Old 11-06-2013, 06:57 PM   #5
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Essentially what a water change does is mimic the constant supply of freshwater that you would encounter in a lake, river, or stream. Because aquariums are a closed environment without this constant supply of fresh water, WE being the aquarists assume the role of mother nature. As stated above, plants complete a huge part of the nitrogen cycle. Even though your parameters are still reading good, there are several unmeasurable parameters in the tank that are either being depleted or building up, much in the same way that when water evaporates in a saltwater tank, the salt concentration rises. I am a firm believer that water changes are the single most important thing one can do for a tank. In 15 years, I have found that a weekly 30% water change is a good balance between practicality and functionality.
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Old 11-06-2013, 07:03 PM   #6
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I turned to EI long ago basically I DIDN'T want to test. Testing gets old really quick, plus your dealing with inaccurate readings many times.

When you dose EI your estimating the needs of the plants. By changing the water your keeping things within a certain range. There's nothing really in EI dosing that is going to hurt your fish unless the amount your using is way off the chart. The other side to a water change is keeping the organic levels low in the tank. The are many way to dos this, but nothing is as free and easy as a water change to keep things within range. Too much organic content will cause algae problems in most setups
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Old 11-06-2013, 07:05 PM   #7
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Quote:
Too much organic content will cause algae problems in most setups
The alternative to this would be to use RO water instead of normal tap.
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Old 12-10-2013, 01:14 AM   #8
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Another reason to do water changes frequently... fend of cyanobacteria.
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