> Hello All,
>
> I am new to the mailing group and to the internet. If I stuff up with
> the etiquette please let me know, it is not intentional.
This list is generally pretty quiet so I would not worry all that much.
>
> Why change the water? Yes, I know, if you don't the fish die, the plants
> look like sh#t, etc. How do I know when I am changing the right amount?
> Yes, I know, look at the fish and you will know. I have no doubt that
> these answers are correct but my curiosity will not let it rest at that.
I think that there are some other things that can help indicate when the
right amount of water is being changed. In my experience when the water
has a weak yellow colour it is off and needs changing badly. I had a bad
attack of glandular fever and my water was not changed for a goodly while
and when the water was that sort of colour I started losing fish. The
National aquarium here had water like that all the time and they are
unable to keep fish alive long term.
>
> Next I started redecorating the house which involved moving the tank. In
> the past I have noted that if water changes have been to few a sudden
> large change will kill the already stressed fish. With this in mind
> backed up by my natural instinct to measure everything. I went and
> bought a Nitrate test kit. Because of everything that I have read about
> the Nitrogen cycle, (end product Nitrate) I expected the reading to be
> through the roof. The Nitrate level was undetectable, pH was 6.8. Now
> confused but not distracted from what I believe I know I did ten percent
> water changes every second day for three weeks before moving the tank.
> When I moved the tank I reused 30% of the original water. All of the
> fish survived.
My three footer is able to use about 1g of N per day with high light
and CO2. You did not say how much attention the plants got, if you were
pruning the plants at all, you were getting rid of a goodly percentage of
the nitrogen that had entered your tank. Additionaly if the substrate
became anaerobic it may potentially have provided a denitrator function
and that is why you have the low readings.
>
> Now curious I decided to do a few experiments. With the tank now stocked
> and feed at more normal levels I maintained a reduced water change
> routine, ten percent a month. I expected the Nitrate level to rise.
> Still undetectable. I bought a new kit (what a waste of money!!) same
> result. I am unwilling to continue with reduced water changes to prove
> that the fish will die well before the Nitrate level rises to even
> 10ppm. If you accept that this will be the end result then the reason
> for water changes is not to reduce the Nitrate level. Then why?
>
I think that nitrate is really only a general indicator of the tanks
performance and that it is only loosely tied to the unknown "bad health"
factors. The content of uric acid and Biological oxygen demand is in my
opinion a better measure. The acidity of a tank is related to the
stocking and feeding levels, high stocking and high feeding mean that
rate of acid production in high (particularly as filtration is an
acidifying process anyway). Biological oxygen demand is a measure of the
rate at which oxygen is consumed in the tank. Generally higher rates of
BOD are not so good. Many of the "I had a healthy tank and then all my
fish died" syndrome is caused by the BOD suddenly increasing because the
tank is stirred up, I can think of at least three cases of this happening
this year. This drains all the oxygen out of the tank and the fish die,
the trick to telling what it is is by looking at the stems of the plants
in the tank the next evening, if they are black in patches they have
suffered oxygen debt (swords are particularly susceptable).
> My attention has now turned to phosphate. Yes, the phosphate level
> definitely rises in my tanks. I have resumed normal water changes (30% /
> month). The phosphate level is about 10ppm. The level in Canberra's (I
> live in Canberra) water supply is about 0.4ppm.
Try for less than .1ppm, algal blooms can be set off by phosphate
readings that are that high. It is also a nutrient that seems to be less
needed than Nitrogen by aquatic plants and so it tends to accumulate and
cause the aformentioned algal attack. I also live in canberra and the
readings that I have got are much less and the official reports say that
phosphate is less than .005ppm.
>
> At this point I would like to make three points. I am NOT recommending
> that anyone change their water change routine. I am NOT suggesting that
> it is necessary measure any of these quantities. I AM interested in
> hearing from those who have done their own experiments in these areas.
This almost sounds like a legal disclaimer, this list is much cleaner
than that.
>
> I have the following questions
> - What effect does phosphate have on the fish?
Very little, although an algal bloom caused by elevated phosphate levels
can kill the fish
> - What level is OK for the fish / plants?
See above but less than .1ppm is desireable
> - What other substances (of interest) accumulate in a fish tank?
Too many to mention individually and the rates vary from one setup to
another and is very dependent on large number of variables. I would say
that some simple organic molecules would accumulate in an over stocked
tank with little maintainance. Ions like Ca, Mg and perhaps Na. Sulphate,
Chloride and Nitrates would also increase while bicarbonates and CO2
would decline.The concentrations of Fe, K and some others would be in very
short supply.
> - How do people living in places like Adelaide get on? Is the nutrient
> level in the water supply high?
Have fish that can take the natural water, use tank water (as I
understand that a lot of adeladians do) or buy an RO unit to clean the
water up.
> My interest is in things that can be measured and proven rather than the
> abstract even though the later may in the end be all we really have to
> make our decisions by.
Absolute measurements are very hard to come by in this game. It takes a
long time to get a tank to a stable system and every tank has its own
peculiarities. Just ask someone who grows plants and has different ones
prospering in different tanks although the general perameters are the
same for both tanks.
>
> To those who have managed to read this far, thank you.
Reading it is a breeze, trying to answer the questions with any sort of
finality is the hard bit
Peter Hughes