I see it recommended, but never explained why. Are there risks, and if so, what are they? And when is a full water change permitted?
What is the idea behind changing only part of a tank's water?
- Thread starter 1commander
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fish waste=ammonia, nitrate, nitrite, phosphates=bad. cycling in fresh water keeps those levels low or none. changing all the water is too stressful on the fish and unneeded unlest major complications arise
You run the frisk of 'shocking' the fish, causing undue stress because your water parameters (mainly, pH, KH, GH) have drastically changed in a very short amount of time.
That's why it's best to do 50% WC each day for 2 days, or even 2x in one day, rather than 100% once.
If something got into the tank (chemicals, coffee, too much food) is about the only times that 100% WC would be beneficial.
That's why it's best to do 50% WC each day for 2 days, or even 2x in one day, rather than 100% once.
If something got into the tank (chemicals, coffee, too much food) is about the only times that 100% WC would be beneficial.
Why doesn't a filter handle all of the ammonia and so forth? Is changing the water necessary if your filters are heavily overpowered for your current aquarium? Say like a FX5 on a 10 gallon aquarium? I don't really get the necessity of changing water except that, obviously if there are bad things in the water, they come out with the water you take out, but I would think those bad things are supposed to stay in the filter, or settle to the bottom of the tank, so taking water off the top is not very effective.
The idea is that a filter is not magic and if you lived in a tank and ate and peed and such in the tank that it would get dirty. There will still be harmful things in the water... so you remove water and add new water... you do not take all the water to keep from losing all the beneficial bacteria that breaks down as much harmful material that exists.
Bacteria in your filter converts ammonia (from fish waste, food etc.) to nitrite and then nitrite to nitrate. Nitrate is the least toxic of the three but essentially there are no bacteria in your filter that can remove it - so you have to do it with water changes.
By only changing part of your water at one time you give the fish a chance to gradually adjust to changes in water composition - which prevents shock.
I suggest you google for "aquarium nitrogen cycle" to get a good understanding of what is happening in your aquarium.
By only changing part of your water at one time you give the fish a chance to gradually adjust to changes in water composition - which prevents shock.
I suggest you google for "aquarium nitrogen cycle" to get a good understanding of what is happening in your aquarium.
A 100% water change is technically best for the fish as it removes all nitrate, etc... It would not shock the fish if of course you did not have to move them. The only way it does shock them is if your temp is different, or your tank is not cycled. The only reason not to do and why I do not do 100% water changes is because that would require netting them and moving them. That would indeed shock them. I do 70-80% water changes once a week on my heavily stocked 125 cichlid tank. The idea that if you change too much water it shocks the fish is not true unless done incorrectly. The more clean water, the better. The beneficial bacteria is not in the water, it is in the bio-media of the filters. Rinsing those out with tank water is what shocks the fish.
twhittle;1180093; said:
I agree.
IMO the key words here though are "unless done incorrectly". If you know what you're doing and are aware of the relevant water chemistry it's safe, but in a neglected tank, to suddenly do a large water change blindly could be disasterous!