Freshwater water change, 70 gallon tank

[thelearninggym]

I have a 70 gallon fresh water tank with approximately 12 fish (or 35 inches of fish), some of these fish I have had for years (Tinfoil Barb, Silver Dollar, Parrot, Pleco, Rainbows). This tank has been set up for many years too. I did a 40% water change yesterday and it seems that still today all my fish are trying to get air at the top of the tank. I have two air pumps, a 400 Fluval filter, and to stone air rocks, have added slime coat and water treatments too, what should I do?

[James]

What are your water conditions such as PH, NH3, NO3? I do a 50% water change each week on my tanks with no problem so I would think something has gone off.

Did you by chance clean the filter at the same time? I dought it is an O2 problem with the air stones, as they disturb the surface which aids in keeping the O2 lvl up.

[CACAdmin]

Hi & :Welcome: I moved your post here to enable you to get some input as quickly as possible.

I don't know if you have substrate in the tank or it is bare bottom. If you have a substrate, did you happen to do a gravel vac when you did the water change? On an established tank often a lot of noxious gasses can build up in the gravel over time(especially if it is deep gravel) and suddenly be released when doing a gravel vac.

[blainep]

What is your water source ?

You may want to test your tap water, possibly something has changed (example - extra chlorine or a switch to chloramines etc)

Maybe try adding a media bag with activated charcoal in it to absorb anything that may be in the water. ( be sure to rinse the charcoal well before adding it to the tank)

If you have any test kits, they might help to determine what's going on.

The only other things that come to mind right now are a PH crash or your bio filtration got damaged and is causing the tank to cycle.

[Melody]

I think pretty much everything has been covered here.:smile:

If water supplies are getting low they will often up the chloramine in water supplies that use it, so that could be it. Double or triple dechlorniator will fix that up. I'd do another change with triple dechlorinator and make sure it removes chloramine as well as chlorine.

I'd definitly test the parameters. Your fish are also growing and you have a lot of deep-bodied fish and/or messy fish in there, so the system will be taxed which sets you up for fluctuations and an unstable enviroment. If your bio filter changes or load increases slightly, it can be enough to throw you into a mini-cycle. Inches are only a guideline for very small bodied fish, like Neons. A spike could also be your problem, based on that, so increasing the waterchanges until it's settled down again will help there. With a heavy fish load, investing in the 'Ammonia Alert' product would also be a good tool so you can keep an eye on it.

Good luck!

[OldMan]

If the 40% water change was because water changes had not been done for a while, it could be old tank syndrome. If that is the case, give the fish a chance to recover before changing any more water.