water changes - by the numbers? - The Planted Tank Forum
 
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post #1 of 10 (permalink) Old 10-27-2014, 03:48 AM Thread Starter
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water changes - by the numbers?

One of the main reasons we do water changes (wc) is to reduce nitrate build up. Other reasons include replenishing carbonates, magnesium, calcium and other forms of hardness..

Assuming I have a calibrated nitrate test kit (I have), as well as GH, KH, and pH tests.. Is there any reason to to a water change as long as these numbers are all normal? I know the biofilter/plants can consume carbonate, dropping KH and pH, and plants can consume calcium/magnesium driving down GH. Thus I am specifically watching for drop in KH, GH or pH, as well as rise in Nitrate.

I'm considering reducing my wc intervals, as I currently do not dose nitrate, and don't want water changes to drive my nitrates down too far.

Of course the common EI approach is to do the wc and replenish the nitrate by dosing... but is postponing the wc and letting nature take its course also a valid approach? Or is there some other parameter I'm missing that builds up or gets depleted?
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post #2 of 10 (permalink) Old 10-27-2014, 04:24 AM
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Hi mattinmd,

I look upon water changes as a way to increase all available minerals for both my fish and my plants and decrease the amount of wastes (including nitrogenous) and dissolved organic matter in my tanks (which some say contributes to BGA). An interesting fact I have witnessed personally is that fish fry do grow faster if given regular water changes compared with few of no water changes. In nature, rivers and lakes are constantly resupplied with fresh water from rains or water coming downstream so water changes is my method of trying to replicate what happens in nature.

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post #3 of 10 (permalink) Old 10-27-2014, 04:48 AM
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You can do water changes by the numbers, and you can adjust input so the numbers balance out to zero water changes.

However, I also see the fish acting much better after a water change, so I still do water changes, even though without water changes the NO3 is stable.
However, in my case the GH and KH are going up. Plants do not use very much, and topping off with tap water is adding more minerals than the plants are using.
So there is another reason I do water changes.

So... how about... decide that X% per week is a good water change (At least it gives you some aquarium water to rinse out the filter media).
Now dose just enough ferts so that X% water change will reset the base amount of nutrients so your dosing is just right. ('Dosing' could be fish food, does not have to be fertilizer)
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post #4 of 10 (permalink) Old 10-27-2014, 04:52 AM
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Test kits can only tell you that something is wrong, they can never guarantee that everything is right.

There are a lot of things in the water we can't test for. Reducing the number of waterchanges you perform could be fine, but I'd be watching more than just the test kits.


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post #5 of 10 (permalink) Old 10-27-2014, 06:10 AM
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Quote:
Originally Posted by mattinmd View Post
One of the main reasons we do water changes (wc) is to reduce nitrate build up. Other reasons include replenishing carbonates, magnesium, calcium and other forms of hardness..

Assuming I have a calibrated nitrate test kit (I have), as well as GH, KH, and pH tests.. Is there any reason to to a water change as long as these numbers are all normal? I know the biofilter/plants can consume carbonate, dropping KH and pH, and plants can consume calcium/magnesium driving down GH. Thus I am specifically watching for drop in KH, GH or pH, as well as rise in Nitrate.

I'm considering reducing my wc intervals, as I currently do not dose nitrate, and don't want water changes to drive my nitrates down too far.

Of course the common EI approach is to do the wc and replenish the nitrate by dosing... but is postponing the wc and letting nature take its course also a valid approach? Or is there some other parameter I'm missing that builds up or gets depleted?

I'm not so sure anyone has shown an upper range that we know is detrimental for NO3.

I've gone 6-12 months without water changes on many tanks.
But,m dirt, muck, post trimming effects, rearrangements, leaf litter, etc, general clean up stuff, are the main reasons.

But there's a more obvious reason as well: do the plants grow and look better after a water change?

I do not think many would ever say "no".

I can go months without cleaning a filter, years on a wet/dry filter.........
I can also automate a water change, try automating a test method sometime.
Cost is another factor, I can change the water pretty fast manually. I still need to clean a prefilter sponge filter, net out leaves, trim plants, wipe glass, remove dirt, dusty mulm etc. Test kits do cost some $, and frankly.............can you name me a single person who got into the hobby to test parameters?

Even one?

Never found one in over 35 years.

You nag folks till the cows come home and they simply WILL NOT CONSISTENTLY MEASURE WITH TEST KITS. Sure, a few do, but the vast majority will do it only if they see a problem and even then, few will bother.

Hobbyists hate testing.

It's easier to have them do a water change.
Most are okay with this, this is something they signed up for and they can see the fish and plant health responses post water changes. Not so much post test kit readings

So at least you get a reward for the work from the water change.
This has much more to do with people's habits and goals than the water change/build up.

change this tank 2x a week:




But this tank only once a month or so:







Regards,
Tom Barr
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post #6 of 10 (permalink) Old 10-27-2014, 01:32 PM Thread Starter
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Ok, I think I need to clarify:

I am NOT looking to eliminate water changes. I am looking to reduce their frequency.

Let me introduce some numbers here, so there's a bit less guesswork going on.

Currently, I do 20% water change weekly. My fish load is relatively light, and I've got some decent plant quantities.

At this rate of water change, my nitrates barely reach 10ppm by the end of the week. I realize there is no established safe level, however this is about half the nitrate that EI folks dose in a week, not even counting any extras from their fish.

I am considering switching from weekly to every other week, which should still keep my nitrates under 20ppm. I'd test nitrate/kh/gh on the off-weeks, and do a change if nitrate >10ppm or if KH isn't 4 (where my tap water sits at), or if GH is more than 1 degree off from the 11 I started at, or if the tank is just getting dirty from leaf litter.


So, given this more constrained scope, and not something obviously foolish like "once a year as long as nitrates are under 80ppm"... does this seem reasonable?

I should also note the tank is low-medium light, daily glut, no CO2 injection, modest dosing of P,K, and micros based on EI low-light profiles.

Last edited by mattinmd; 10-27-2014 at 01:38 PM. Reason: added tank notes.
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post #7 of 10 (permalink) Old 10-28-2014, 05:23 AM
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We are not all alike in our approach to planted tanks. Some of us can use an incentive to do routine tank maintenance. If we change water weekly, we can either sit around waiting for the tank water to drain out, then sit around waiting for the tank water to fill back up, or we can use that time to clean the tank glass, pick out dead plant debris, prune, look at all plants for problems, etc. Oddly enough those are good routine maintenance steps. So, one could say a weekly water change is an incentive to some of us to do better tank maintenance.

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post #8 of 10 (permalink) Old 10-28-2014, 06:42 AM
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Quote:
Originally Posted by mattinmd View Post
Ok, I think I need to clarify:

I am NOT looking to eliminate water changes. I am looking to reduce their frequency.

I should also note the tank is low-medium light, daily glut, no CO2 injection, modest dosing of P,K, and micros based on EI low-light profiles.
Under this type of routine, I typically suggest 1/4 to 1/3 EI, not 1/2.
Water changes typically run once a month.

Once a month say 50% is better than 2x a month of 20% regarding any build up of any nutrients.

And it's nearly 2x less work. You should harm no buckets in the process, if you use buckets, you are doing the water change the wrong way. Takes but 5 more minutes just once and you are done.

Dosing, maybe 2x a week. Some go 1x a week with this method.
Plant species: chose a few fast growers , but mostly slower growers.
Keep the fast growers well trimmed. Glut at 5 mls per 10 Gal of tank daily.
Good current, clean filters every other week or once a month as needed.
Adding water to counter evaporation will be an issue. Then a bucket might be used.

A garden hose with a PVC J hook can drain and refill the water once a month.



One end goes outside to the grass or landscaping plants, then after draining to the desired level, you take the same drain end and hook to the shower head with a 1/2 to garden hose connector(they have these at Home Depot)

Once you established your desired goal/method, then it's much easier to give you or anyone a simple routine. Plant tanks run the gambit from low light/no CO2/Glut etc, to high light and lots of CO2, and everything in between. No one method will suit all tanks.

If you are not adding KNO3, then I would also add GH booster once a week, maybe add around 1/2 degree of GH. It's got some K2SO4 in it, about 50% by weight.

50% water change makes the math for dosing EASY also.
Assuming the tap water is zero ppm, the max build up due to dosing will be no more than 2x the dosing you did between the 50% water change.

Say you dosed 10 ppm over 1 month of NO3 as KNO3, the maximum possible build up would 20 ppm in the aquarium with a monthly 50% water change. Now, you no longer need to test or measure, you know you are within the 20ppm or less upper range. All you need to worry about is dosing too little.

This way you can further reduce the labor(fewer, but larger water changes, no testing).

If you'd like to model the outcomes of EI dosing versus time and build up, see here:

http://rota.la/ei/

Note, if you go under optional, you can use known uptakes and even fish food % by weight of N and then use a 90% wasted N factor for the N produced from fish waste.

Also note: EI's 50% water change is entirely arbitrary, it's a simple method and the math is easier for most using 50% weekly.
It really depends on how much build up potential excess you are willing to accept.
Same with the frequency of water changes.
Generally, you maximize the dilution to labor ratio by doing larger % water changes, vs many smaller ones more frequently.

Once you start a water change, may as well go big if you have a freshwater tank(or a Marine tank for that matter).
Does not take that much longer to do 20% vs 50% once you drag the stuff out and start the job.




Regards,
Tom Barr
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post #9 of 10 (permalink) Old 10-28-2014, 07:07 AM Thread Starter
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Tom and hoppy,

Thanks for the advice, both of your points make quite a lot of sense.

I think I will stick with weekly, or close to weekly, just from a plant litter standpoint. I could see going to 2 weeks, but not a whole month before I'd want to vacuum a bit.

As for buckets, I only use one 2 gallon bucket in my water changes, and the rest is done using a tap-to-tank changer (python). I use a 2 gallon bucket to dilute the dose of prime and GH booster sufficient for the volume of my change, pour a bit in before I start the python, then slowly pour the rest in as the python runs.

Last edited by mattinmd; 10-28-2014 at 07:12 AM. Reason: added more thoughts from Hoppy's post.
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post #10 of 10 (permalink) Old 10-28-2014, 10:19 AM
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I must be the odd one out, then...I actually don't mind testing. *G*
My water has TDS of about 12 out of the tap, and I change 50% every 8-9 days. Since this is a 32 USG growout tank for youngsters, I see that they benefit from the pwc's. Lots of plants, too. Aften pwc, I test nitrate, GH, pH, iron, potassium, phosphate and add only what is needed to keep the plants happy. Nitrate-dosing is almost never necessary....it usually it comes out around 10 after pwc and works its way up a bit in the interval, due to much feeding with live foods. Needing KNO3 usually means I have neglected to trim my plants . The tank has medium light and daily glut dosing. Works for me :-)

Humans may rule the world...but bacteria run it..
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