Moving To A Bigger Tank, But Want To Leave Snails Behind

Thank you both for explaining and suggestions, it makes sense. I think I'll transfer the whole filter over to new tank to speed up the move process. I'll run both filters alongside for a couple of weeks then move the filter media to the new filter. Where should I place the media in the new filter, in place of the coarse sponge? Here is what I have:

1. Poly pad
2. Carbon sponge
3. Nitrax
4. Coarse sponge
5. Cirax
6. Fine sponge x 2

I like to have these little Physalis snails in all of my tanks. Whenever I do a water change, I "vacuum" the gravel, but there's never anything to vacuum up, even after 4 or 5 weeks. I feed my fish well, more than most people I think, but the snails are pretty effective at cleaning up solid waste. I do believe you get less problems the more complex the ecosystem in your tank i.e. fish, plants, various bacteria, snails, even algae (to a certain extent). More complex systems are always less prone to sudden change.

Quote from: Sue on June 11, 2014, 02:25:14 PM

Keep the carbon sponge in the cupboard in case you ever need it.

I've previously been advised to keep carbon sponge in a sealed plastic bag when not in use - unsure whether this is good advice or not?

I suppose the carbon could adsorb airborne things if it's left out of a bag. My carbon granules came in a plastic tub with a lid, so that'll keep mine away from the air.

So much useful advice! I rather spend the money on the fish and plants then on swapping the sponges.

As I've got the carbon sponge running for a week now, I think I may as well run it for a month. I heard somewhere that once you activate it by immersing in water it will work for this period of time then stop or start releasing back the chemicals it absorbed. I've got two more sponges so I'll keep them to the side and use when needed.

There are a lot of myths about carbon.

It adsorbs (not absorbs) by covalent bonding. Adsorb means things attach to the surface only, while absorb means they penetrate inside. Carbon doesn't form ionic bonds so it doesn't remove ions like nitrite, nitrate or ammonium - and the majority of the ammonia in the tank is in the ammonium form. Carbon mainly adsorbs organic chemicals, such as medication and tannins from wood, though it will also adsorb such things as hormones secreted by the fish and even plants.

It doesn't release chemicals wholesale into the tank. When it adsorbs things, there is always some left in the water. There is an equilibrium between the bound and the free. If the equilibrium is disturbed the chemical will move on or off the carbon to restore the equilibrium. So removing medication, it will bind to the carbon but some will be left free in the water. You do a water change and remove some of the free so some has to come off the carbon back into the water to restore the equilibrium. That's why the carbon should be thrown away a couple of days after using it to remove meds. Also, using several smaller batches, changed every day, will remove more of the med.

Some things are more strongly bound to carbon than others. Although carbon becomes 'full' within a few days to a couple of weeks, if a medication binds more strongly to the carbon it will push off whatever is already on there and stick in its place. This does two things - it removes the med from the water and it releases possible toxins back into the water.

The reason so many filters include carbon is a hangover from decades past. Then, the nitrogen cycle was not understood. And fishkeepers rarely did water changes, which resulted in the water turning yellow. These fishkeepers did not like yellow water so they used carbon to remove it. That's all filters were back then, an air powered box filter containing carbon granules and a bit of filter wool to stop the fish poo etc getting into the carbon. Because the carbon got full and the water started turning yellow again, they had to change the carbon regularly so that no bacteria cultures had time to grow on the carbon, though there would have been some on the other surfaces in the tank.
We now know about the nitrogen cycle and have filters which provide homes for the bacteria. We now know that regular water changes are good for the fish. But carbon is cheap to produce, it has to be changed regularly and filter manufacturers have a nice little earner, so why stop putting it in the filter packaging?

That's good news. Nice one!