Water change

[Grete Gillebo]

My first Parosphromenus groups are “installed”, 4 different species. Most were quite young, but Helene let me have a breeding pair of P. linkei 🙂
One week after arrival, the P. linkei male was guarding eggs. This tank is due for a water change, I have been postponing this so as not to disturb him or the eggs.
So what do all you experienced breeders do, water change or no water change at such times ?

[helene schoubye]

I am quite sure people do different things.
I wouldnt worry about a waterchange, – I have often done it, and then afterwards realised there were eggs in the cave, or very young fry.
The thing is, – when I do a waterchange, I dont clean or any such thing, – I do a small waterchange only, – maybe only 20 procent or so. I leave everything as it is in the tank, leaves etc.
Of course, its good to be very careful and not stir the water too much.

Another thing which could be said, is also, – that depending on what kind of tank it is, – perhaps it isnt really nessesary to do a water change ?
I dont do waterchanges every week at all, – in particular not in tanks with few fish, theres really not that big a need, in my opinion. So, depending on the situation in your tank, you could also choose to leave the water change a little bit.

[Rafael Eggli]

Hi,

personally I have never experienced any problems with water change. Linkei are really tolerant with such disturbment. They are only very vulnerable regarding the parameters of the water, especially temperature. If the water is too cold they will stand still and behave almost “shocked frozen”. Mine could after such an event luckily recover quite well. This is also true for eggs and/or fry! They will not like a “shower of fresh water through their cave but as long as you keep the nest out of direct water movement, everything is alright!

I think that the most important thing with keeping fish is waterchange no matter what species and i always change at least 50% of the water every week. I am convinced that this is a very essential point because of simple mathematics:

There is a constant flow of pollution into the tank from food, debris and the fish’s metabolism. These accumulate during a waterchange period and are then partially removed. The important word here is partially: If before your water change you have, say 1 gramm of pollutant xy in the tank, you will remove only a fraction wich is in line with the fraction of the whole volume you remove. So if you then change 20% of the water you will end up with 0.8gramms after the waterchange. However, in the consecutive period there will be another 1 gramm added to give a total of 1.8 gramms of which you then take out another 20% which leads to 1.44 gramms and so on…

week 3: 1.952g
w 4: 2.3616g
w 5: 2.689g
w 10 3.57g

From about week 16 we are getting close to the upper limit where there is no more significant increase of pollutant xy. Its about 4 gramms. This is huge since when compared, we find that it is the same as if we had not done any waterchange for 4 weeks!!!

Now this is surprising and should be alarming. but what if we do the same for another amount of waterchange?

Say again, 1 gramm of pollutant xy is added but we do 60% Waterchanges:
week 1: 0.6g
week 2: 0.96
w 3: 1.176g
w 4: 1.3056g
w 11:1.46g
w 30: 1.499999668g

Seems like we have a limes (limit which is never reached) here again! But what surprise: its only about 1.5 gramms!!!

now what about 50% waterchange?
w1: 0.5
w2: 0.75
w3: 0.875
w4: 0.9375
w5: 0.96875
w6: 0.984375
and so on… limes: about 1 so we end up with the constant amount of 1 gramm pollutant xy.

seems cool, right? By simply increasing the amount of water we exchange, we can have significantly better results!!! and they are sooner reached so there is a lot less time in which the amount is strongly changing -> our fish can get ued to it sooner! what if we really go for it and do 70% waterchange?

w1: 0.3
w2: 0.39
w3: 0.417
w4: 0.425
w5: 0.42753
w10: 0.4285688979

WOW within only 4 weeks to a constant rate of about 0.43 gramms!!!

This has to do a lot with mathematics and numerical sequences. In facht, if you have “real data” of any kind, you can run the calculation yourself with any a bit more sophisticcated smartphone-calculator app or with old-school calculaters. Even my Texas Instruments-30 worked well here 🙂

The equation is:

a_n=(a_n-1+c)*q

with:
a_n: the amount of substance xy after n weeks/periods
a_n-1: the amount of the previous week
c: constant net inflow of substance xy (in the uper examples it was 1 gramm that came in every week) within the period
q: the fraction of the water that remains IN the tank (in my first example it was 0.8 since 80% of the water remained there) so it equals 1-the percentage you are changing.

Actually, you can also use it if you want to calculate how much fertilizer etc. your plants need to keep a certain level of plant nutrients.

Now this has gotten very long. I hope you are not bored but I think it is best to show with examples why I do the waterchanges the way I do them: 50% because the whole total will never get above the amount that would be added within 2 weeks which I find an acceptable thing.

Of course this is not a very sophisticated model of the Aquaria but it might give a reasonable idea of how we should choode our Waterchange-ratios.

[Joshua Morgan]

Does that mean that 20% water changes are insufficient for paros? (I guess this also means that paro fry lack the notorious sensitivity fish fry have to water changes…I’ve heard that doing water changes on fry of some species can kill all the fry from shock).

[Rafael Eggli]

Hey,

I would not say that this is insufficient but personally, I prefer high volumes of exchange water instead of slowly but surely increasing concentration levels.

Actually, the ratio between the final top point (called limes in mathematics) and the constant inflow c only depends on the amount of water changed. This means that for whatever substance you want to know about the Limes, you can always take your c and multiply it by the corresponding limes (4 for 20% water change, 1.5 for 60% wc…)

So I think with the really diffficult paros we should be aware that large waterchange ratios will be dangerous. BUT: the same thing we have discussed above can to a certain extert also be applied for germs! And we want to keep the concentration of germs low. Assuming a linear growth for germs is reasonable since low ph effectively slows down the reproduction rate of the bacteria and fungi so the natural exponential growth is pushed down. And it is mainly a high germ pressure that kills young eggs and fry of paros…

I let everyone decide for themselves how much water they want to change but it can help a lot to understand the models available for the description of our nature and aquariums

[Pavel Chaloupka]

Hey everyone, I would not worry about water changes being dangerous. I have done many changes in tanks where I did not know clutches were in and nothing wrong happened. And I have to say that I do really big changes, sometimes even 80+% of water exactly for the reasons that Rafael stated. I use prepared water with stable pH and I care about the temperature being the same, but still if you do this to susceptipble fish, you would certainly experience problems. And after freeswimming, the fry is even harder, so after this experience, I even raised Paros fry in small bowls and changed 1/2 a water twice daily to get rid of hungry rotifers before replacing them with fresh.

[Peter Finke]

You must think like this: The aquarium water is always worse than the flowing blackwater of the wet rainforest. The best conditions for our Paros would be slowly streaming fresh waters. But in the normal tank this is not possible. The more often you change water and the more you change big quantities the better. But normal aquarists are lazy. They change every four days or every week a certain part of the old water. The more you combat your laziness and change more often more water the better.
Fortunately, most of our Paros are able to stand the medium standard changing conditions, but that does not mean this to be good; it’s more or less acceptable only. The problem is that of a structure quite different from nature: the aquarium. Water change is an imperfect means to imitate the constant flow of best waters without germs. The more you fight your laziness and change more frequent and bigger quantities, the better. If you succeed staying lazy and change little, you can be lucky with certain species, but you will probably not with other. At any rate you play with the adaptability of organisms that are far less adaptable than most of other aquarium inhabitants.

[Dorothee Jöllenbeck-Pfeffel]

According to the fact, that our tanks are a lot of different to a natural slow floating river, I decided again to give the tanks some air, ether by little bubble stones or by oxidants.
As well I experiment with shrimps in my group tanks (not in the breeding tanks) to keep the tank more clean. At the moment I have two tanks with caridina parvidentata and in my tank with Sphaerichtys selatanensis I have a group of very resistant Red Fire.

I make 50% water change once a week.

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