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I think you might have misunderstood me. I posted that video as an example of successful large water changes. I would never do 90% because it would freak the fishies out. max I would do is around 60% because it gets cumbersome after that for me and for the fish. that is why I prefer "smaller" but more frequent with one large change.

im going to see if I can get more people to understand the benefits of water changing because the fish being alive or dead or sick or well are not good indicators.
I feel it should be dictated by the color, size, behavior, and awesomeness of the fish.

basically people should stop doing water changes for their fish to survive and start doing them to get their fish to thrive

its bad enough we are keeping the fish in their glass houses we should at least give them the best treatment possible like a child. sure you can feed that kid crap and only allow him to bathe once a week he will survive but he will look like some kind of hobo

I am a big believer in take care of the water and the fish will take care of themselves.

I do 50% water changes on all my tanks every 4th day.

Hi nico,
You hit on a distinction I try to impress upon people and that is that there is a big difference between keeping your fish well enough that they survive and keeping your fish so they are thriving.
Fish which are merely existing are not likely to spawn much but if they are thriving then they breed much easier and when fish spawn regularly that is the best evidence that they are thriving.

If anyone is practicing minimal water changes because they use buckets I strongly recommend you invest in either one of the commercial drain and refill systems or a hose and GardenHoseThead(GHT) adapter for your faucet so you can get away from the hard work of using buckets.

Hi I do 30% water changes every four days half R/O and half treated tap water.
I heat the water to exactly the same temperature as the existing water in my tanks as all my plecs are happy and I have very very low loads in my tanks and BIG filtration and I do not want to stress my fish I think this is adequate.

nicofish wrote: he favors large water changes every two days. while I favored 20% once a week. we both run Fx5 he on a 55 gallon and I on a 75.

what do you guys do? as far as water changes go.

I assume you mean a Fluval FX5, that is a huge filter for a 55 or 75 tank I use it on my 240 gallon and do 10% water change twice a week. I also vac the gravel once a month and clean the filter every 3 months.

50% every 2nd day ....

Hi all,

Whilst I understand the principle of this, I'm not entirely convinced this works. If you have low KH/GH, and the nitrate level goes up, I think the CO3+ ions are (to some extent) consumed during the nitrification process, so the TDS value stays about the same, but water has deteriorated in quality. ....

This is correct for the oxidation of NH3 to NO3, I'll ignore the CO2 <> H2CO3 equilibrium, so: NH3 + CO2 + 1.5 O2 → NO2- + CO2 + 0.5 O2 → NO3- and as NH3 turns into NO3 we have 3H ions "spare", 2 bond with an oxygen to form H2O and one is released as H+, the cause of bio-acidification.

The details of the differing way that salts and acids effect TDS is in the graph in this post, together with a description. <http://www.planetcatfish.com/forum/view ... 0&start=20>. In planted tanks in TDS terms you can, to a large degree, ignore the effects bio-acidification, I don't keep unplanted tanks so this may be a more relevant factor in them but I don't think it will make much difference.

cheers Darrel

I think the essential thing here is the 'rate of pollution' if that's the term for it. If, simply, you start with a base pollution level of 20 in the tank, the rate of pollution is +10 per week and your replacement water is 5 then by the end of the week you have to make a 50% water change to get back to the 20 you started the week with.

There are a few variables here, but I'm pretty sure someone with a bit of maths could stick it all in a formula.

The starting level, rate of increase and replacement water levels should all be easily measurable.

Or am I missing something?

Yes, it's all possible to calculate, and what you say is along the lines I follow.

And to sum up the thread so far:
1. There is, generally, no harm in changing large volumes of water or making frequent water changes.
2. Bigger water changes are better.
3. More frequent water changes are better.
4. Bigger water changes are needed for heavily stocked tanks than lightly stocked tanks.
5. The goal is to keep GOOD quality water for the fish, so that they thrive, not just survive.

I don't think there is any "controversy" in this...

There are of course practical implications - if you have to spend 24 hours per day doing water changes, you may want to consider doing it somewhat differently...

In my case, I use RO water, and as a consequence, I can't do as many or as large water changes as I like all the time, because I only have 2 x 25g loft tanks for RO storage (and my 75 gpd takes about 2 days to fill those tanks!)

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Mats

I use the python water change system on all mybigger tanks. wonderful.

I think larger frequent water changes benefit the fish immensely.

I choose 50% every 4th day on my bigger tanks to keep the NA at around 5 ppm.

My small betta ten gals i do once a week 50% to do the same.

Just wondering if anyone does water changes based on actual volume or just a percentage of whatever your tanks stated volume is? When I say actual volume that would be the amount of water in the tank after subtracting all your substrate and decorations from your total volume. I see alot of math and chemistry being thrown out there and as you know in math and chemistry starting with an accurate base is essential.

As for me I don't do the math or chemistry. I took my tank and sharpied a mark at the -10% & -20% total volume levels. My method is crude, measure the tank hieght, then divide by 10 and each increment is 10%. When I water change I just take out somewhere between those 2 marks and I'm good.

With that said removing 10% volume from the top of the tank takes out more water than 10% measured from the bottom. My example is: 240 galloon tank 10% = 24 gallons & my Tank height is 31 inches so 3.1 inches = 24 gallons. When removing water from the tank the top few inches have no plants or decorations so the 24 gallons or 3.1 inches is at 100% actual volume. If I were to continue as I began to hit the levels where decorations come into play the 24 gallons would be greater than 3.1 inches because that volume is displaced by the decorations. The last 3.1 inches at the bottom of the tank would maybe hold 5 gallons because I have 3 inches of gravel and that gravel takes up the majority of the volume.

So when you say you do 50% water change in a 240 tank are you saying you would replace 120 gallons? I only ask because there were so many comments about percentages of pollutants that are removed based on a 7 day schedule. Obviously those percentages would vary greatly when comparing a heavily decorated tank versus one that is sparsely decorated. The same would apply to no substrate, gravel, and sand as sand displaces the greatest volume.

I hope someone understands my explaination it sounds simple to me but it may not come accross the way I have it worded.

I just take out "rougly half the height of the water" to make a 50% change. And yes the decorations can make a difference. The other day I took most of the wood out of one of my 270 liter tanks, and the water was about an inch lower - on a tank that is 16" tall...

--
Mats

I do the same as Mats.

I put my heaters horizontally at the 50% line by sight and empty to just above it then refill.

Almost all river fish can handle large (80%+) water changes. IME only some lake fish (ie;Tanganyikans)do not handle large water changes well.

I rarely have more than 1/4 inch of substrate so when I remove 75% it is 3/4 of the water inside the tank. If allowing for the inside dimensions then I am probably removing closer to 70% actual volume. The actual inside volume is almost always slightly less than the advertised volume.

The main point is to have some regime and sufficient volumes of water changes to keep wastes, minerals and a stimulating effect on the fish. Too much of a change, especially when using fresh tap water which is treated with a water conditioner almost at the same time as you are making the water change can be a bit much for some fish. For me the safe and beneficial amount is about 70% to 75% every 4 days. It doesn't matter if you skip a day or vary the volume slightly. Having some regular regime is what matters. And small amounts daily doesn't cut it for me. Neither does a daily 90% change unless the new water has been conditioned(chlorine/chloramine neutralizer) and aerated at least 12 hours.

OK, using a hammer to crack a walnut and all that, I got my son to have a stab at a water change formula. We used the term pollution, but measuring nitrate levels would be sensible. This is what he came up with:
If:
Ps = pollution level at start (can be measured), example 20
Pe = pollution level at end (can be measured), example 30
Dm= number of days between measuring Ps and Pe (known) example 7
Then:
Pd= (Pe-Ps)/Dm (this is the rate of pollution per day, assumed to be linear), calculated from above examples as 1.43
Also:
Vc=Volume to be changed (in litres), to be calculated
D= number of days since last water change (known), example 10
Pc=pollution level of fresh water used for change (can be measured), example 2
Vt=total volume of tank (known), example 300
So:
Vc=[{Ps-(DPd)}/{Pc-(DPd)}] x Vt

Using the above example: Vc=[{20-(10*1.43)}/{2-(10*1.43)}] x 300 = -139 litres
So after 10 days without a water change in a 300 litre tank you would need to change 139 litres of water to get the level of pollution back to where it was at the start using the above parameters.

I know it will never be used but we both had fun doing it!

RickE wrote:Vc=[{Ps-(DPd)}/{Pc-(DPd)}] x Vt

I know it will never be used but we both had fun doing it!

I applaud you & your son for taking on such a task. Pat the boy on the back because most kids would rather play video games, and that includes a lot of kids over 20, lol.

Just to clarify I'll break it down by steps for those who don't understand or forgot most algebra, feel free to check my math, it's been a couple decades for me too.

Step 1. subtract Pe-Ps then divide that by Dm = to get Pd
Step 2. multiply (number of days) which is D x Pd = to get DPd
Step 3. (on the left side of equation) subtract Ps-DPd
Step 4. (on the right side of equation) subtract Pc-DPd
Step 5. the answer from step 3 is divided by the answer from step 4
Step 6. the answer from step 5 is multiplied by Vt

In addition for more accurate volume, measure the inside of the tank to get the true volume.
Also if you want to get the volume of your decorations fill a vessel (bucket, tub, etc) with a known volume of water lets say 20 liters for smaller objects. Then mark a line at the water height. Next submerge your decoration in the water and mark another line at the new water level. Now remove the water until you have subtracted back to the original water line. Then remove the decoration from the water and using a measuring cup fill the bucket back to the original water line you started with. The amount of water you measure back into the bucket is the volume of your decoration.

andywoolloo wrote:I do the same as Mats.

I put my heaters horizontally at the 50% line by sight and empty to just above it then refill.

That's a great tip with the heaters, I always unplug them for 15 minutes before doing a water change on my kids 10 gallon tanks (I think thats around 35-40 liters). That is one of those things you see and then wonder why you never thought of it. I'll never unplug a heater again, THANKS.

joefish72b wrote: Pat the boy on the back because most kids would rather play video games, and that includes a lot of kids over 20, lol.

Thanks Joe. It happened to be a perfect combo - he's studying further maths and I love fish!

It is really commendable your son and you worked through the math.
You know exactly what is necessary to maintain your target level of maximum nitrates.
All this has been done before for the aquaculture industry.
The bottom line is the old axiom, The solution for pollution is dilution.

I am also impressed with the time and energy put into the mathematical figures!

and you're welcome on the heater idea. I got paranoid that I would forget to unplug one or plug one back in. which is what happenned , i forgot to plug one back in so i was all hmm,let me just fix that so i don't have to mess with that!

And here I thought all the while the idea of designing submersible heaters was to lay them along the bottom out of sight.

nice formula !!! I enjoy just thinking of these things not so much the experimental aspect so well done. I believe the math is right tho who am I to say im just a high schooler.... <-- me except I have a lot of rather unkempt hair...

either way if I am not mistaken there is a web site that most likely uses this formula as it asks for similar variables (as far as I can remember haven't the site in a while) also it graphs the amount of waste to show you how your "pollutants would rise or drop" according to the water change schedule ill pull it up if I can find it.

I love this thread you are all very knoledgable I just ahd an argument with a non believer in WC it was good there was a microbiologist there to back me I win!!

hmm you mind if I add a piece to the formula just for fun? ill work on it today ill use stoicheometry to calculate the moles of nitrite entering the tank based off of the ammount of chlorine and dechlorinator used. hmm only problematic part is getting the formula for the dechlorinator once I have that its just a matter of balancing the equation and finding moles.

I have seen that or a similar cart.
Another way to approach it is how much food do you feed in a given amount of water because it is usually close to 2% per 24 hours of the weight of the fish in grams.
Some estimates have to be used but the calculations only need to be in the ball park.
Extreme precision isn't necessary.

ehhh, im just doing it for kicks

but I cant find what chemical is used in dechlorinators it cant be vitamin b beuase that doesnt result in NH3 even though it is used to dechlorinate. if anyone knows what the chemical is please tell me. that way I can add the ammount of ammonia or subsequently (lol did I use that word right) NOx.

plus my formula only took like ten minutes to wrote


so to reiterate

*can someone get me the chemical used to dechlorinate water in say prime. one of the products must be ammonia
*and I will need the molarity of chlorine in water as well

thanks

Hi all,
Seachem won't tell you what is in Prime, but you can use the patent for Kordon AmQuel to have a pretty good guess. <http://www.novalek.com/archive/kpd58.htm>.



cheers Darrel

The amount of ammonia in the tap-water, assuming it's at the absolute limit of chloramine usage will only be about 2ppm - which means that it adds about 1 ppm NO3 if you do a 50% water change. [That's not entirely true, as NO3 is a heavier molecule than the ammonia, but essentially, it's a small amount].

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Mats

Most use sodium hypochlorite, same "Hypo" used in film development to neutralize the chlorine.
I do not know what they use to break down chloramine which is the more persistent and dangerous chemical widely used in public water supplies.

Hi all,

Most use sodium hypochlorite

Yes, this is to neutralise the chlorine, the newer, "better" conditioners use EDTA and sodium hydroxymethanesulfonate (or similar). The EDTA chelates any heavy metals (as long as Fe ions aren't present in large amounts) and the hydroxymethane - end of the molecule reacts with ammonia to form a non-toxic, stable water-soluble compound "aminomethanesulfonate". The sulfonate end of the molecule reacts with both free-available chlorine, and combined-available chlorine in chloramines. Any ammonia (from the break down of the chloramine) is then mopped up by the sodium hydroxymethanesulfonate.

Personally I keep well away from tap water (other than for drinking), but I'm lucky to have a plentiful supply of fairly clean rain water.

cheers Darrel