Long-term water clouding problem

The water in my tanks has been really cloudy (brownish-yellowish-greenish) for over a month now. I have been doing weekly water changes and switched from an undergravel to a stronger external filter about a week ago, but it hasn't helped much. Any thoughts on the cause/solution? Thanks!

Ashley, do you clean your gravel weekly with a gravel syphon? It could be a bacteria or aglae bloom?

Please tell us about your set up water quality, temperatures, types of weeds etc.

I do clean the gravel weekly, at the same time as doing the water change. There was a lot of gunk trapped under the undergravel filter, but I cleaned that out when I switched the filters a week ago and it's still cloudy.

It's a 10-gallon tank with one axolotl, no plants, temperature usually around 20 degrees, pH about 6.9. It does get a lot of light, could that be it?

There are usually causes for this, all of which cause algae or bacteria to bloom. We can rule out an issue of too few water changes. To much water changed can cause it. You shouldn't change more than half the water in your tank at once, especially in a newly setup tank, because it can upset the balance of your tank. Other causes could be overfeeding, too much light, too high a temprature. On that is often overlooked is wood. Do you have any kind of wood or branches in your tank? They could be rotting, or leeching tanins into the water.

Ashley - Green water it is caused by too much waste in the water. Since you cleaned up under the under gravel filter and are vacuuming the gravel the green water problem should resolve with weekly water changes.

But...
Since you cleaned under the under gravel filter and are now vacuuming the gravel and added a new filter you may be going through a new tank cycling.

To much changing of water at this point will slow down the cycle time. You should test your tank water for ammonia and nitrite and take appropriate measures. If your ammonia and or nitrite is high it would be best to remove your axolotl from this tank to a smaller container and change its water in that container as needed until you have your tank straightened out.

If everything tests out ok and the water will not clear in a few days, it could be your gravel. I have had "bad gravel" before that was causing cloudy water.

What kind of external filter did you buy?

Additionally she has switched filters at the same time as a massive water change so this will also disrupt the cycle of the system.

Ed