Why am I changing water?

colinsk

colinsk

On the fringe...
Dec 18, 2008
444
0
0
Ca
www.designerinlight.com
Hi everyone. I have not posted to this forum before. I usually post in the newbee forum however I think this question more belongs here. This is my first aquarium. (Although I have since started working on a 10 gallon.)

I have a planted 29 gallon aquarium that shows lots of growth daily. I am using 55 watts of light with a very good reflector. I have no signs of algae so far. The aquarium was set up at the beginning of December. It is heavily stocked with animals and plants. I am using DIY CO2. My reactor is simply an inverted container that catches CO2. I have no filter just a power head that does not disturb the surface of the water. The water is crystal clear.

I am using pea gravel with laterite as a substrate and I have 20 watts of substrate heating.

I had been doing twice a week 33% water changes. About 3 weeks ago I decided to stop water changes for a while and see what the paramaters were. They have been constant, day or night, for 3 weeks:

0 Ammonia
0 Nitrite
0 Nitrite
pH 7.4
gH 7
kH 5

I have not been measuring phosphates till tonight:

.5 PO4

So, here are my conclusions that I want to run up the flag pole here. I am running very low CO2. The tank seems to be both nitrogen and carbon limited. Since, I do not add any ferts the only source of PO4 and N is from fish food. I choose my feeding based on what the plants want and not what the animals eat. The tank is densily planted enough that many of the fish don't notice I am feeding.

In the long run will having an excess of PO4 create algae problems?

My tap water is very high in Mg. It is about 43ppm this time of year. The PO4 will attach to the Ca and the Mg and try to precipitate. The PO4 lost to Ca as calcium phosphate is lost to the system. The phosphate tied up in Magnisium Phosphate is about half soluable. So the phosphate in the water column represents a fraction of the PO4 in the system.

Whew... So that leads to my question: Why am I changing water? If I am looking to lower the PO4 then I really only need to be doing a gravel vac to remove the precipitated PO4. Is there another reason to change water?
 
in most rivers and lakes they have an inlet and an outlet. in a fishtank (or atleast most) dont have this. doing water changes will help with fish health in the long run.

and also doing water changes will induce some speices to spawn!!!
 
What we measure with our test kits, such as nitrates, are hazardous to our fish but they are not the only harmful chemicals that build up in our fish tanks. They also, more so in a non-planted fish tank, act as indicators to warn us to change the water before things get really bad. If you let it build up and only top off water loss due to evaporation, you are asking for old tank syndrome. So, it is important to change the water for that reason. Another reason, is there are some things in the water, such as trace minerals that can be helpful to your plants. Since you are not adding ferts to your tank, water changes will be beneficial in replenishing these.

Plus, fresh water is nice. Think of it this way, a closed room with re-cycled air is livable, but how nice is it when you open the window, let out the stale air and replace it with fresh air? Really nice! lol.
 
Most low tech aquariums don't change their water often, only several times a year. You can check out several of these at natural aquarium dot com.

This only works on low tech, heavy planted tanks, with low stock.

To answer your question, water changes is not necessary if you have a balance.
 
just out of curiosity, is there a reason why you have chosen not to have a filter on the tank?
 
rocker92 said:
in most rivers and lakes they have an inlet and an outlet. in a fishtank (or atleast most) dont have this. doing water changes will help with fish health in the long run.

and also doing water changes will induce some speices to spawn!!!
Click to expand...

Don't get me wrong, it is not that I am planning to stop water changes I am just wondering what my task is so that I amy perform it better.

Not changing water makes the aquarium behave more like a marsh than a stream. There are thriving eco systems in a marsh as well as a stream.
 
Bunny13 said:
What we measure with our test kits, such as nitrates, are hazardous to our fish but they are not the only harmful chemicals that build up in our fish tanks. They also, more so in a non-planted fish tank, act as indicators to warn us to change the water before things get really bad. If you let it build up and only top off water loss due to evaporation, you are asking for old tank syndrome. So, it is important to change the water for that reason.
Click to expand...

The best description of old tank syndrome I can find is here:

http://www.bestfish.com/oldtank.html

The first problem he describes in high nitrate, my plants are taking care of that one. The second is crashing pH. Water changes will help replentish the buffer. I have added a handful of oyster shells as an insurance to "excess H ions". (I describe this in different terms. Over time the temporary hardness (kH) is converted to CO2 and lowers the pH. It is the same thing.)

The third, rising hardness from evaporation. This is one of the best reasons I can find to do water changes in a heavily planted aquarium. Topping off is not a viable solution unless you have distilled, RO or DI water.

In some rarer situations, notably in "natural" or some reef aquaria in which plants, rather than bacteria, are the primary nitrogen consumers, the inhabitants could be suffering even if nitrate and ammonia readings are very low, and pH steady or a bit high. Rarely is any aquarium so well balanced that no by-products are accumulating and no necessary elements are in decline.
Click to expand...

This is closer to the system I am describing even though it is fresh water. There is no way for me to assay alll of the ingredients of the water. However in another post I will try to make some simplifications and see where we get.

Another reason, is there are some things in the water, such as trace minerals that can be helpful to your plants. Since you are not adding ferts to your tank, water changes will be beneficial in replenishing these.
Click to expand...

These minerals are also not leaving the tank. Of the 19 elements that living organisms need all of them are contained in fish food. We need to make sure that the trace elements are not being bound and are available to the plants in on form or another. It would be best to study the chemistry of each of the seperatly as there are so few.

Plus, fresh water is nice. Think of it this way, a closed room with re-cycled air is livable, but how nice is it when you open the window, let out the stale air and replace it with fresh air? Really nice! lol.
Click to expand...

A very good point indeed! This directly releates to the DOC comment and I'll try to address it as well.
 
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