i have a problem with my freshwater fish tank?

Question

The water in my freshwater fish tank has gone funny? It has developed like a film on top which i have tried to remove with kitchen roll but it just comes back! I have also noticed that the water smells stale and it has gone partly cloudy. I did a half water change,Cleaned my filters but still it is the same. Can anyone help please!
I have a juwel rekord 70 ( 18gallon)
It has been running since last november.
I have 6 pristilla tetras,1 fighting fish and a catfish.
I clean it fortnightly with a gravel cleaner. I also use stress zyme and water conditioner.

Answer 1

I agree witht he possibility of slight over feeding. The film you are seeing is usually the result of excess protiens and fats in the water and the cloudiness and stale smell are the result of excess bacterial growth (feeding off the decay of the fats and protiens). A 25% water change weekly would help cure the problem as will replacing the carbon in your filter or starting to usse carbon if possible.

MM

Answer 2

It's some organic pollutant. Perhaps it is the fish food, if it contains a lot of fat? It can also be due to overfeeding. Be careful of oxegyn deprevation as bacterias uses oxegyn in their process to break this down. I would bet that the gravel at the bottom contains a lot of organic matter. Try stirring a bit in the gravel to see if this is the case. (Other pollutants may be tree logs inside the fish tank that are decomposing).
If you see a lot of dirt coming up when you stir the bottom you should clean it out. If it's possible, try to keep most of the water in other contaniers and keep pouring in new, fresh, water, then stirring and removing the dirty water. Do this until it's clean.
*I typed this answer before you added your new information.
I suggest that you check if there's any dirt under rocks etc., if you got any. :)

Answer 3

You are probably feeding too much - most often the cause of problems in fish tanks of all types and sizes.

I would suggest you add some activated carbon - your filter may have a compartment for it, if not just put it in a mesh bad and hang it in the tank. This will act as a chemical sponge and remove any nasties.

If you used tap water for the water change it wouldn't have helped as most city tap water is pretty high in Nitrate which is the chemical that algae and plants live off. To get around this use RO water or filter the water through carbon (not as effective) before adding it to the tank.

Laters

Answer 4

Simple case of bacterial bloom which can be caused from a number of things. First being, when you are cleaning your tank how much water are you taking out of the tank? you should not remove more than 25-30% cleaning your tank out totally, you run the risk of destroying the beneficial bacteria.

Bacterial bloom can be caused by overfeeding as well, however this isn't in most cases unless you really over feed. Also, check the food you are feeding your fish. You never want to have fish foods that contain more than 8% fat. (Or oils)

Also, cleaning too much does not allow the beneficial bacterial colonies to remain stable. This is usually called stalling. Once a week or once every two weeks for cleaning (depending on your tank) is all you need.

Answer 5

It sounds like a simple case of algae. You can never get rid of it completely but you can reduce it by not having the light on as often. Do not do more frequent water changes as too much of this can stress out your fish and lead to deaths. Unless you get to the point where it is stopping you being able to see the fish then I wouldnt worry about it.

Answer 6

Why don't you just ask your local fish shop??