Water Change Amount

andy53 · 09-29-2006, 12:23 PM

I have read in many different places, and talked to many people and everyone has a different idea on how much and how often to do a water change. Is there any good rule of thumb about what percent to change and how often? I guess the most popular I have heard is 10% once a week, but I've heard 10% every 3 months or 50% a week, etc., so I don't know what is right. Any help would be appreciated.

thewebpop · 09-29-2006, 01:10 PM

If I suggested anything to you, it would be just another number out there. I change 25% weekly in my 20 Gal. I feel since you have such a small tank...
This might best be answered by Jay or Aaron.
Good Luck, Pop's

Jay · 09-29-2006, 02:50 PM

Let's look at why water changes are important.

Water Quality is the Answer

No matter how good our filtration system is, or how well behaved our fish are, there will be a gradual decline in water quality over time.

The aquarium is a living, organic environment, with a ton of creatures sharing the same space. Bacteria (lots of varieties) Fish, Algae, Protozoa, all are excreting waste and dander into the water. We pollute the water with food, additives, water conditioners, fertilizers for our plants, medications, etc. etc.etc.

All of this contributes to an increase in organic compounds dissolved in the water (TDS/DOC), as these dissolved compounds increase it can cause fish health to decrease from the toxic nature of overexposure.

A good tool is to test your nitrates, if nitrate concentration is elevated say above 10 ppm ,in a non or lightly planted tank, that is a good indication that your TDS is probably elevated and a water change should be done.

I use my tanks as an example:

75 gallon
Heavily Planted
Moderate Fish Load
I dose (add) Potassium Nitrate, Potassium, Calcium, Magnesium, Phosphates,
Seachem Excel, as plant Nutrients. I dose these nutrients in excess of what the plants will use in order not to bottom out on any one.

I also feed a mixture of frozen foods which are excellent poulters.

In order to prevent accumulation beyond what is good for the plants and not harmful to the fish I change 60 - 70 % of the water WEEKLY without fail.

I change the 20 gallon guppy tank about 40% weekly because I can not get a handle on how much is enough and tend to over feed the fry and shrimp. That amount keeps me out of trouble with TDS, cloudy water, algae etc.

I change the Betta tank 50% because it is such a small space, and quickly deteriorates.

Your mileage may vary and is not cast in stone, You know you need to change some, 70% will not hurt you, determining what amount returns your water quality to excellent is part of the fun of the hobby.

Hope this helps

Jay

andy53 · 09-29-2006, 07:39 PM

That does help, but like Pops said it's just another number, I guess the key is figuring it out for myself.

thewebpop · 09-29-2006, 07:49 PM

Jay.... Ya Gotta-Luv-em!

Reminds me of a school teacher from years back... answers your questions with questions to make us LEARN AND THINK!

Why give the answer when you can give a lesson! Thanks Jay, your answers always help us learn too!

Later, Pop's

Tommy Gun · 09-29-2006, 08:09 PM

Great point Pops! I was thinking he is more like one of those karate teachers who make you wax their car to figure out how to fight. That makes no sense to me, but Jay's answer is a good one.

I dont think it will be too hard for you to figure out how much water to change. I would just stick to some sort of schedule and try to do the smallest amount of water you can, above 10% or so. When I first started out, I had a 55 gallon tank that came as a kit with almost everything I needed to start out. The kit came with spacific numbers and times for water changes, which is ok, but not always needed. I would test your water for the first couple times before changing any water. I would think that if your tank is cycled, your water is going to appear ok to you, depending on the tests you are using (I highly suggest you use the test tube type, they are more reliable and less easily spoiled by humidity like the test strips are). So, even if your water is ok, you might want to change 10% anyways to help reduce algea spores and just other junk that you are not testing for. I like to think of it more as getting some stale water out and putting in some fresh stuff. I wouldnt want to sit in the same bath water for weeks at a time, so I like to think my fish appreciate it as well.

I wanted to reply to this thread to express an opinion and see what Jay or anyone else has to think about it. IMO, it is possible to change TOO MUCH water at times because you do not want to take out too much of your bacteria's food and bacteria itself. I think that changing 70 percent of your average, non planted, non overstocked fish tank water could really hurt you and keep your tank in a constant cycle since the bacteria is being reduced and not being allowed to reestablish itself. I bring this up because I read one thread (not sure if it was on this site or another) in which a person had added fish too soon and did big water changes to help keep the fish alive, but she did it for almost a year. The end result was a tank that had been running for a year, but never completely cycled.

Anyone have thoughts on this opinon of mine? I know Jay's tank is somewhat the exception because it is planted and he needs excellent water conditions as well as nutrients that most tanks do not need. I say that because I am not going against his answer, but trying to get some input for those of us who are scared of growing anything above water, not to mention below it.

thewebpop · 09-29-2006, 09:10 PM

I would think the bacteria is within the filter, gravel, walls of tank and attached to plants. I would not think the water would contain the colonies themself ? Not sure just my "Ole" brain trying to think (I know that is not a good idea to think Ha)
Later, Pop's

Loman · 09-29-2006, 10:20 PM

Tommy, Pop's,
I think that both of these concepts could be correct. I do not believe that the water is itself hosting much (if any) of the bacteria. It does have the nutrients that the bacteria needs however, so if you take the bacteria's nutrients out of the tank it follows that the bacteria will likely die. Coupled with that most people vacuum the gravel when changing the water so they are also disturbing the gravel where a lot of the bacteria live. That mechanical action seems like it would cause the bacteria to get swept out as well then and have the same effect of depleting the bacteria.

The other thought that seems like a big factor is that most fish need some level of stability (often stability is more important than the actual value of a given parameter) It seems like massive water changes are not really conducive to having stability because you are changing so much at one time. Even simple things like water temp would be more challenging with a big water change. Personally I prefer to do smaller more frequent water changes but I am not sure I could prove that is better.

Jay · 09-30-2006, 11:01 AM

DOC / TDS = the amount of dissolved organic compounds, bacterial waste, fish waste, additives, nitrates, phosphates, salt, protein, chlorides, etc. etc. which accumulate in the aquarium and over time contribute to the decline in water quality.

The beneficial bacteria (the bacteria that feeds on ammonia, and then on the nitrite waste from that colony and finally produces nitrates as waste) The ones we waited on a month to grow, are not free swimming. THEY DO NOT live in the water column.

It is impossible to vacuum them out when you vacuum the gravel, They are not scraped off when you clean the glass.

Trust me on this one, They stay put.

Quote:

I wanted to reply to this thread to express an opinion and see what Jay or anyone else has to think about it. IMO, it is possible to change TOO MUCH water at times because you do not want to take out too much of your bacteria's food and bacteria itself. I think that changing 70 percent of your average, non planted, non overstocked fish tank water could really hurt you and keep your tank in a constant cycle since the bacteria is being reduced and not being allowed to reestablish itself.

The nitrifying bacteria above consume ammonia from the fish bioload almost as fast as it is produced. Same with the nitrite. The left over is Nitrate.
The nitrifying bacteria colonies will grow only as big and as fast as their ammonia source. The beneficial bacterias food is always available in the tank as long as there are fish. Therefore it can be surmised that an increase in TDS and other pollutants is not necessary for anything, and is probably not a good thing. I clearly do not want my PO4 (phosphate) levels to be 12 ppm in my tank, and in an unplanted tank you want only a trace. Water changes accomplish that.

There are some common sense issues with water changes such as...

The temperature should be close within a few degrees
The same water source should be used
The water should be treated for chlorine, chloramines, and toxic levels of heavy metals.
GH and KH levels should be maintained.

Can Large Water Changes Be Harmful To Fish ?

In a word YES...but not the way you think.

The reason for a water change is to restore water quality and to reduce the DOC (dissolved organic compounds), restore essential electrolytes (mineral balance), allow us to vacuum up pollutants on and in the gravel, etc. etc.

Quote:

The other thought that seems like a big factor is that most fish need some level of stability (often stability is more important than the actual value of a given parameter) It seems like massive water changes are not really conducive to having stability because you are changing so much at one time.

The goal here IS to maintain stability, Stability in excellent water quality, not stability in high levels of potentially toxic DOC (the pollutants and dander I talked about earlier).

Here's the killer --> A tank which has been neglected in terms of water changes, or not enough water is changed will continue to have a gradual increase in DOC. Fish can adjust to this, it IS harming them, but they can adjust and stay alive and seem to be OK.

OK now you get it! In this situation, when you step in and do a big change, the fish are unable to adjust rapidly enough to the change in osmotic pressure and die. In other words the change in their environment is to rapid to adjust to and they go into shock. Like YOU going from a blood O2 level of 99% to 30% in a few seconds. <--- Man that is major stress!!!

Consistency and routine then becomes the issues. You want to change enough water to maintain excellent water quality (reasonable levels of DOC) and do it often enough so as to not cause any osmotic problems.

Therefore, like I said before, a good tool is to check your Nitrates. If they are elevated above 10 ppm in a nonplanted tank, then your DOC is probably high also and you need to change some water. Your mileage may vary as to how much.

Hope this helped
Jay

thewebpop · 09-30-2006, 11:59 AM

Good Information, Thanks to all that contributed their thoughts and info!
Later, Pop's