Fish Tanks - Top-Up

[Mr-H]

My son's fish tank seems to have a reducing amount of water. Very slowly, by evaporation(?) the water level is going down. Can I take out (say) half a pint of water, add half a pint of tap water to it, leave it for an hour or so, then add that back to the tank? It has been suggested that maybe as much as half the water in the tank needs to be removed, and then combined with new to re-add. This to me seems long winded etc.

[aelmpvw]

i thought mine was due to evaporation until i found a tiny leak

[beejaybee]

Evert couple of weeks I take out about 1/2 the water in our tank & replace it with fresh water.

[EDDIE51]

Do not use water straight from the tap, get a container and fill it with water then leave it 24 hours and then use it to top up. Tap water has Chlorine in it and can harm or even kill the fish, letting it stand allows the Chlorine to evaporate.
We used to have fish tanks and always kept a supply of water in 5 litre containers ready for top ups. You do need to top up regularly as water will evaporate , it is worse it hot weather as it evaporates faster.

[divegirl]

Going to play devils advocate here....

I just use tap water for a top up. Here's why. If you are running a well established tank the bacteria in the filter should be more than capable of removing any nasties and as long as it's only the odd litre or two it is easily diluted into the water column anyway.

Lisa x

[wildwood]

There is such a thing as watershock with fish. If your fish have been swimming around for months in polluted water, changing half the water suddenly may set some into shock. Depending on the size of your aquarium, better to remove half pint and add one pint fresh straight out of tap (don't add the half pint back in) until the water is up to the level you want. If the tank is more than 10 gallons, double the amount removed/added.

I change 10% of the water weekly and never overstock the tanks.

[hammerman]

Wildwood, absolute b011ox.

As with Divegirl, ive always used water straight from the tap. I top up around 6 gallons a week from my 5 foot, high tech planted tank and i just throw it in....sometimes im not even bothered about temperature (tropical fish often breed when the water gets cooler....it simulates the rainy season) Ive also never used dechlorinator.

Oh 40 years keeping trops, reef aquaria, koi and a 70,000 gallon pond at work.

[wildwood]

Hammerman, you're such an idiot, In your eagerness to make me look a fool you have in fact supported my post. 10% of a 5' tank is around 6 gallons.

I don't know why or what I have ever done to you. You have been continually trying to belittle my meagre contributions for years. Do you have some sort of disorder?

Your continual boast of btw 40 years experience merely means you are a bighead, not that you know anything.

[hammerman]

Wildwood, you have always given cr@p advice, often dangerous. It's almost like something on here comes up and you go and look it up online or in a book.

Watershock ??? what a pile of horses*1t