Hi please help. My tank is just under 2 metres long and I carried out a large water change, just under 50% taken out.

After I had topped the tank up again (using Aqua blue for the chlorine), I noticed tiny little air bubbles on the surface of most of my fish. There were also air bubbles on the plants and on the inside of the glass on the top half of the tank - these gradually disappeared after a few hours. I usually associate air bubbles on the inside of glass with setting up a new tank and you have to wait until it's 'settled in' before adding fish. I havn't carried out this large a water change for a while as it worked out to just under 200 litres of water. I usually conduct a 30-35% water change every week. I left my filters on and the light, turned off the heater and the submerssible.

My question is - on a tank 180x60x50 (cm), can a 50% water change create a 'new tank syndrome' for the fish? They appear happy enough today but I've honestly never seen this before!

I'm not ignorant - I have 3 kids and want to make sure my baby oscars live to a ripe old age!

Many thanks!
Amber

I shouldn't worry about the bubbles, I've never had a problem in any of my tanks. I don't often see lots of bubbles on the fish, but Occasionally they are there. I don't know the exact reason, but it's got something to do with oxygen and gases getting trapped in the water as they run through your pipes, when it enters your tank, the bubbles are still there. People often think their water is turning cloudy, this is just tiny bubbles that will soon dissipate.

Whereas I don't recommend huge water changes [60% upwards]as long as you use something to remove the chlorine/chloride,large water changes shouldn't have a detrimental effect on the biological filter if it is well established. if you are putting the water straight into the tank from the tap, I would advise you to turn the filters off until the tank is completely full and the water conditioner has had time to do its work, then put the filters back on again. I don't like leaving the filters running and having water running through them when it may not have been treated properly. Most treatments remove chlorine instantly so you shouldn't have anything to worry about

Dont worry about the bubbles as they are harmless. I sometimes get a few on my fish if they swim through the fresh water as it refills my tank

Thanks very much, one can't exactly ask the fish how they're feeling so a water change should be as uneventful as possible!!

Thanks very much for your assistance!