Water change Size

[pateceramics]

I wanted to sit down and do the math for myself, so I thought I'd share...

If you change 10% water per week:

Week #
1 100% new water
2 10% new, 90% 1-week-old
3 10% new, 9% 1-w-o, 81% 2-week-old
4 10% new, 9% 1-w-o, 8.1% 2-w-o, 72.9% 3-week-old
5 10% new, 9% 1-w-o, 8.1% 2-w-o, 7.3% 3-w-o, 65.6% 4-week-old
6 10% new, 9% 1-w-o, 8.1% 2-w-o, 7.3% 3-w-o, 6.6% 4-w-o, 59% 5-week-old
7 10% new, 9% 1-w-o, 8.1% 2-w-o, 7.3% 3-w-o, 6.6% 4-w-o, 5.9% 5-w-o, 53.1% 6-week-old
8 10% new, 9% 1-w-o, 8.1% 2-w-o, 7.3% 3-w-o, 6.6% 4-w-o, 5.9% 5-w-o, 5.3% 6-w-o, 47.8% 7-week-old water

Holy cow! If you only change 10% water per week, after faithfully changing water for two months, you still have almost half same water you started with. With the addition of lots of fish pee. Poor fishies!

Let's try 25% water changes:

Week #
1 100% new water
2 25% new, 75% 1-week-old
3 25% new, 18.8% 1-w-o, 56.2% 2-week-old
4 25% new, 18.8% 1-w-o, 14.1% 2-w-o, 42.1% 3-week-old
5 25% new, 18.8% 1-w-o, 14.1% 2-w-o, 10.6% 3-w-o, 31.5% 4-week-old
6 25% new, 18.8% 1-w-o, 14.1% 2-w-o, 10.6% 3-w-o, 7.9% 4-w-o, 23.6% 5-week-old
7 25% new, 18.8% 1-w-o, 14.1% 2-w-o, 10.6% 3-w-o, 7.9% 4-w-o, 5.9% 5-w-o, 17.7% 6-week-old
8 25% new, 18.8% 1-w-o, 14.1% 2-w-o, 10.6% 3-w-o, 7.9% 4-w-o, 5.9% 5-w-o, 4.4% 6-w-o, 13.3% 7-week-old


Much better, but after two months of changing water, I still have almost 15% of the water I started with, along with all the pee that has been added to it.

Let's try 50% weekly water changes!

Week #
1 100% new water
2 50% new, 50% 1-week-old
3 50% new, 25% 1-w-o, 25% 2-week-old
4 50% new, 25% 1-w-o, 12.5% 2-week-old, 12.5% 3-week-old
5 50% new, 25% 1-w-o, 12.5% 2-w-o, 6.25% 3-w-o, 6.25% 4-week-old
6 50% new, 25% 1-w-o, 12.5% 2-w-o, 6.25% 3-w-o, 3.13% 4-w-o, 3.13% 5-week-old
7 50% new, 25% 1-w-o, 12.5% 2-w-o, 6.25% 3-w-o, 3.13% 4-w-o, 1.56% 5-w-o, 1.56% 6-week-old
8 50% new, 25% 1-w-o, 12.5% 2-w-o, 6.25% 3-w-o, 3.13% 4-w-o, 1.56% 5-w-o, .78% 6-w-o, .78% 7-week-old


That's more like it! By doing 50% weekly water changes, after two months, less than 1% of the water is the same water I started with.

It's important to note that this same cumulative math effect applies to each individual water change. So, to siphon off a bucket full of water, then siphon off a second bucket, and then refill your tank with 2 buckets full is not the same thing as to siphon off a bucket, refill the tank, siphon off a second bucket, and refill the tank. Two 25% water changes are not equal to one 50% water change.

And always be sure when refilling the tank to add de-chlorinator to the water before it goes into the tank, and to be sure that the water you are adding is the same temperature as the water in the tank. Float your tank thermometer in the bucket while it is filling to be sure. One way to euthanize sick fish is to subject them to sudden temperature change. You don't want to accidentally euthanize a healthy one, or make it sick.

Happy cleaning!

 

[IThinkTherefore]

Oh, how I love statistics. The numbers will confess to anything when tortured.

Haha, I'm kidding. But your math is off.

There is no difference between "old" and "new" water. Built-up ammonia, nitrite, and nitrate would be visible in the test results of everyones tanks if this logic followed through.

The ammonia and nitrite are removed by the biological filter, and the solid waste and nitrate are removed by plants or vacuuming.

50% water changes can cause swings in pH and hardness that are tough on fish. The best bet to keep a tank clean and healthy is small (~25%) regular changes. "Old" water and "pee" won't just stay put in a tank with a healthy biological filter.

 

[Kiara1125]

Nice job!! I do 30% water changes at the beginning and end of every week, and, I don't know why, but I find doing water changes as a stress reliever. Yes, changing fish poop water is a stress reliever. lol!! My Neons and Platy fry seem to want to play with other fish then just their own type after a water change.

Attention: I have been able to have my tank in the perfect condition for my Neons to spawn. The eggs get eaten a few minutes after the spawn (I don't feel like raising Neon fry right now), but my Neons are spawning.

Water Test:
Ammonia- 0 (duh!!)
Nitrite- 0 (again, duh!!)
Nitrate- 15
Hardness- 15
Temperature- 74F
pH- 7.2

Well, that's it!! I know that egg-layers usually need soft water around 5, but my Neons were spawning anyway. I think it's because my only flourescent light in the tank blew. It's like: light- ok, dark- SPAWN!!!!!! lol!!

 

[pateceramics]

Hey IThinkTherefore, "Built-up ammonia, nitrite, and nitrate would be visible in the test results of everyones tanks if this logic followed through."

You're right! The nitrates do show up! How many beginners do we see on the forums who have a thoroughly cycled tank, but post with a question because they have a sudden nitrate spike? Lots! And the answer to their question is always, how much water do you change? Change more! And change more often. As you say, the ammonia and nitrite are removed by the "good" bacteria of the biological filter once your tank is cycled, but the only way to get rid of nitrates is a good vacuuming. (I consider a vac a part of any water change and, of course, even just changing water without a vac removes some nitrates. If they stayed politely down in the gravel, they would never bother the fish).

As for old water, new water...I know it's all mixed together in the tank and homogenized, and I know that the cycle bacteria and plants do a lot of cleaning, but this was the best way I could think of to express the concept and encourage people to clean their tanks. There are a lot of people who think that two 25% water changes is equal to one 50% water change, in terms of nitrate removal, and it isn't. And the cumulative effect of that mistake in logic is a big difference in water quality for your fish.

I can't say that I've ever seen any swings in ph in my tanks over the years. And we always do lots of big water changes. The big ph changes that hurt fish seem to come from 1. people trying to change their ph with chemical additives to "make it perfect" for a certain type of fish, or 2. not changing the water for ages and ages until the effects of fish waste, decaying fish food, growth of plants or algae have been enough to slowly change ph in the tank over time. Then when they do finally change some water, their tank ph is very different from the ph of the water coming out of the tap, so, yes, they should do a few small changes first so that they don't shock the fish.

What comes out of my tap has a very consistent ph, so the more often I change water, and the bigger those water changes are, the closer my tank ph stays to the steady ph of what comes out of the tap, and the smaller the swing is with each individual water change.

As for water hardness, I've forgotten how that factors in, although I seem to remember that it was a direct correlation with ph? Remind me?

Sorry if my analogy wasn't the greatest, but it was the best way I could think of to express the concept. Ideas for a clearer way to get it across?

Thanks!

 

[pateceramics]

Kiara1125 Rock on! We've never kept neons, but everything else we put in the tanks over the years seems bent on reproduction. Try cherry barbs if you want some entertainment. We had to take out some plants so that they couldn't hide their eggs from the other fish or they would have taken over.

 

[IThinkTherefore]

More dissolved salts = harder water
harder water = higher pH

Well, I think you hit the nail on the head with why the term "old water" is misleading. I guess I just don't see why full 50% weekly water changes in an established tank are good or necessary when all parameters are in check

 

[skjl47]

Hello; Afraid I have the same question as IThinkTherefore about the need for such large and frequent water changes. Please note. It is not that frequent, large percentage water changes are harmful. The question of how much is gained comes to mind.

If everything was going well I changed water on a monthly schedule for a lot of years. Kept a lot of healthy fish during that time. Even with my experience, I did allowed the posts on this forum to sway me into more frequent water changes over the last months. I simply cannot see any notable difference thus far. Let me state again that there seems to be no harm from more frequent water changes other than a lot more work and the use of a lot more water.

Some are convinced that the frequent/large volume water changes are the way to go. I am still considering the issue. I do know from experience that it is not necessary to do big volume changes every week. Some have posted about feeling the need to do water changes each day. Maybe if they are trying to resolve a problem, but it does not seem necessary under normal conditions.

I tried weekly changes for a while and have been trending toward bi-weekly of late. I know that monthly changes will work after using that cycle for a few decades. You can write it off that I am just that good, but I very seriously doubt it. Two weeks seems to be working well.

 

[webgeek]

50% water change for my platties every 3rd day.

 

[skjl47]

Hello; This seems to be going in a similar way to the recent discussion about stocking density.

Very over stocked tanks and not or rarely doing water changes will lead to problems. That is perhaps the only point of consensus. At the far end of the scale in the other direction, there are the extremes of ultra low density stocking and constant water changes. Somewhere in between are stable points where stocking densities and water changes of some volume and frequency are fine and that going beyond these points adds little to the health of a tank.

I also imagine that these stable points will vary with the size of a tank, the experience of the fish keeper, the quality of the local water, the type of fish, planted or unplanted, the type of filtration and many other variables.

 

[pateceramics]

skjl47, I agree, there are a lot of variables. And that's why I like large, frequent water changes. It's one variable that I can control reliably.

New fishkeepers are going to overstock, or not cycle properly, or put the world's tiniest filter on a 50 gallon tank. It takes long and complicated explanations to help them figure out what is appropriate for their tank because of the many variables involved. But one piece of advice that is not at all long or complicated, and which will help any other issues they have going on, is to do large, regular water changes. I don't feel like it takes much more work to do a large water change than a small one. But the difference in impact on tank water quality is huge.

If your tank is on the edge of an ICH explosion and you do a 10% water change, that is probably not going to put much of a dent in the disease progression. After 8 weeks of 10% water changes, 47% of the water full of ICH spores that you started with is still present in your tank. (See the math above). If you are doing 50% water changes, you have made as much impact with one water change, as you would have with 8. And with very little difference in the amount of work. You filled the bucket all the way instead of part of the way. Or you filled it more than once.

Got algae problems? Larger water changes will help remove algae spores. Got disease problems? Larger water changes will remove more of the bacteria/virus/parasite from the tank and make it easier for your fish's immune system to do its job. Adding some new fish? Larger water changes will help keep your ammonia and nitrite levels in check while your biological filter adjusts to the increased amount of fish waste.

But the main point I wanted to make was that you have to do 8 10% water changes to get the same effect as about 3 25% changes, or 1 50% change. Which is really more work?

 

[skjl47]

Hello; I lived in a placed for a while that had a small year round creek across the road. It came right off the mountain. I envisioned somehow putting a pipe in it upstream and having a constant flow of fresh water trickle in and an overflow to take it out. It never worked out as there was a blacktop road to cross and some else owned the creek. I think some of the big aquariums on the coast constantly pump in water from far out in the ocean.

This has brought a question to mind. The Aquarium at Chattoonoga Tennessee has some big and densely stocked tanks. I wonder how they manage the water? They have a number of smaller tanks in addition to the big ones. Does anyone know?

 

[pateceramics]

I don't know about water changes, but I had a friend in high school who used to volunteer at the New England Aquarium. He got to put on a scuba suit and dive into the "giant ocean tank" with the sharks and sea turtles to scrub the glass with a scrubby aquarium sponge.

Link!
Behind the scenes at the Giant Ocean Tank

 

[nanu156]

marcy hearts skj

Hello; This seems to be going in a similar way to the recent discussion about stocking density.

Very over stocked tanks and not or rarely doing water changes will lead to problems. That is perhaps the only point of consensus. At the far end of the scale in the other direction, there are the extremes of ultra low density stocking and constant water changes. Somewhere in between are stable points where stocking densities and water changes of some volume and frequency are fine and that going beyond these points adds little to the health of a tank.

I also imagine that these stable points will vary with the size of a tank, the experience of the fish keeper, the quality of the local water, the type of fish, planted or unplanted, the type of filtration and many other variables.

So basically i think YOU Are dead nuts accurate here

i dislike posts that make noobs think they dont NEED TO CHANEG THEIR WATER AS MUCH as i dislike posts MAKING THEM THNK THEY NEED TO BE CLEANING NAZIS

ITS LIKE teaching a TEEnager to drive you dont tell them about speEDING and how not to get caught you teach them the rules yeah WHEN YOU HAve been DRivinG A feW yeARs you figure ouT what woRKS what spped you can go on the eway with out getting poped but heck I would never tell a sixteen year old that if you stay under eighty-three
you wont get pulled over i MEAN WeLL THATS JUST ASKING FOR IT

CHange TWENTY FIVE TO FIFTY PERCENT OF YOUR WATER WEEKLYISH IF YOU ARE A NOOB

CHANGE MORE IF YOUR FISH ARE LOOKInG SiCK IF SOMEONE RECENTLY DIed or iF YOu are cycliNg

bETTER FOOD also keeps yoru tank cleaner so maybe consider putting out a bit more for food

sorry about my wonky TEXT GOT A CaPS LocK KeY ACTING uP

 

[nanu156]

Hello; I lived in a placed for a while that had a small year round creek across the road. It came right off the mountain. I envisioned somehow putting a pipe in it upstream and having a constant flow of fresh water trickle in and an overflow to take it out. It never worked out as there was a blacktop road to cross and some else owned the creek. I think some of the big aquariums on the coast constantly pump in water from far out in the ocean.

This has brought a question to mind. The Aquarium at Chattoonoga Tennessee has some big and densely stocked tanks. I wonder how they manage the water? They have a number of smaller tanks in addition to the big ones. Does anyone know?

THEY USE A SYSTEM OF SUMps a PRACTICE COMMON IN SALT WATER AQUARIUMS wheRE THere iS A SECOND AQUARIUM UNDER NEATH THAT HOLDS A TON OF WATER THAT ACTS LIKE A FILTER IN MANY WAYS

 

[pateceramics]

I knew there was something about getting ph swings from not changing your water frequently enough! Here is a nice concise explanation snipped from Orion's excellent sticky on water ph:

"The most important aspect of pH, is keeping it stable. This is best accomplished by performing regular water changes. When water evaporates, only the H2O molecules leave the tank, meaning that minerals and pollutants are still in the tank. If you have a 40 gallon tank, and you loose 1 gallon a day due to evaporation, now you only have 39 gallons of water, but all the minerals and pollutants of 40 gallons. Dissolved solids and minerals are what make a pH alkaline. The more that is dissolved, then the higher your pH is going to be. So if you do not perform regular water changes, then the pH of your tank will increase. But this is not a good way to increase the pH of your water. Like I said above, not only are the minerals left behind, but pollutants are as well. An increase in pollutants can quickly take a beautiful healthy fish and make it a very sad sight to see. By performing regular water changes, this helps to remove minerals and pollutants from your tank, and help keep the pH stable and your fish healthy."

If anyone needs clarification on WHY dissolved minerals make your water alkaline, see the sticky in it's entirety. But the point relevant to this discussion is that there are dissolved minerals in your tap water, and that when water evaporates from your tank they stay behind, building up in higher and higher concentrations, and raising your ph higher and higher. Fish can acclimate to gradual change in ph. But when you finally get around to doing a water change months later, the addition of new water, which will have a much lower ph, makes a very sudden drop in ph in the tank. Which can shock your fish and make them vulnerable to disease. So, if you haven't changed your water in ages, do a series of small daily water changes to slowly lower your ph, step by step. Test your tank ph and test your tap water ph every day during this process. Keep a little log of your results and how much water you changed each day. When you have managed to gradually change enough water that the tank water is the same ph as the tap water again, start a routine of larger weekly water changes so that you don't get yourself in this pickle again.