slippery walls

[scavenger]

When, I touch the walls and surfaces of some of the decorations in my fish tank, they seem to feel a bit slippery like there is some very thin coating on them that i cant see. I'm a newbie who only started fishkeeping little more than 2 months ago and was wondering what is this caused by and is it normal? Everything is normal as far as my fish go.

[cyberbeer65]

It's normal,no cause for alarm.....

[scavenger]

do you know what it is caused by?

[Raskolnikov]

It is the multitude of microscopic and near-microscopic organisms collectively known as the "bio-film". It will vary from tank to tank, and can include fungi, bacteria, algae, invertebrates....etc.

Some bacteria in the bio film reduce ammonia down to nitrite, and others convert nitrite to nitrate. Yes, the very bacteria commonly referred to as "beneficial bacteria" in regard to aquariums.

[scavenger]

Then i assume it is good to have it, right?

[Raskolnikov]

Then i assume it is good to have it, right?

Yes, indeed.

[RTR]

But then BGA (blue-green alga) makes an excellent biofilm also, one of the best, as it recyles nutrients far better than most. So not all biofilms are created equal from the tank-keeper's viewpoint. They are however completely unavoidable - any surface available for attachment will develop some sort of biofilm - so you just accept it, and feel free to remove any which disturb you by their appearance. The majority of your nitrification bacteria should be in your filter, where nutrient and oxygen delivery is at the maximum (read as: water flow). And yes, I have tested that, and 90-95% of the nitrification activity in my tanks is in the filters.

[jaylin]

And yes, I have tested that, and 90-95% of the nitrification activity in my tanks is in the filters.

How did you test that?

[RTR]

All my filters are canisters, so they transplant easily. Condition a newly set tank with a single newly set canister fishlessly. Move canister to another freshly set tank. Challenge both the newest tank with the conditioned canister and the "cycled" tank with with an uncycled filter added. Test ammonia/nitrite/nitrate after 12 and 24 hours. Guess where the ammonia is always oxidized to nitrate within 24 hours? The tank with the conditioned filter, not the conditioned tank (which almost always showed less than 10% of the ammonia challenge gone within 24 hr). I have difficulty testing to 10% repeatability without using the LaMotte tests, so I have to dilute down to the range suited to those tests.

Repeat until you sure it is not fluke. It is not.

Corollary trials from planted tanks: 1)Tanks which are heavily planted and also equipped with biofilters do not rely on the biofilters as much as the plants. If you "borrow" a long-term filter from a healthy planted tank, put it on a new tank and ammonia-challenge it, it will not be competent to handle the bioload of the original tank. But, the long-term filter will mature when fishless is continued in a very short time, as it is well inoculated with the needed bacteria. 2) If you can borrow a comparable filter from a FO tank, use that on a new setup, ammonia challenge that setup and it will be fully competent. Conclusion: Plants out-compete biofilters for ammonia when they are healthy, but they do not necessarily get all the nitrogenous wastes, the bacterial filter gets some.

Try it for yourself. Replication of experimental data is valuable.

Another corollary: It helps to run a lot of similar tanks and a lot of similar filters - it makes "borrowing" much easier.

[zazz]

But then BGA (blue-green alga) makes an excellent biofilm also, one of the best, as it recyles nutrients far better than most. So not all biofilms are created equal from the tank-keeper's viewpoint.
Any way to encourage our favorite biofilms?

[RTR]

Keep the tank clean with high quality water. Excess mineral nutrients and organics can promote the less desirable biofilms such as BGA.