Bio-Media Removed

When I first started my current reef aquarium over six years ago I didn’t use any live rock. Instead, for the bio-filtration I used canister filters.

There are two Eheim Ecco canister filters installed and I have to say that they are good, well constructed and to date absolutely reliable. Anyway that’s not what I’m on about here.

Over the six years many corals on rocks have been introduced and the rock that was inert and dead is now live. It hasn’t the potential diversity of life that natural live rock has, but it has a lot of organisms on it and probably in it – there are tiny tube worms by the hundred and a high population of tiny creatures that appear mostly at night. It is also typical live rock in appearance as far as encrusting algae and the like are concerned. I have to say I can’t see that much rock anyway as most is covered up by some organism or another.

I suspected that the rock was live because of nitrate. As I had elected to use canister filters a home made denitrator had been fitted as well. There has only ever been the tiniest presence of nitrate according to the tests and it was so faint my wife and I were unsure about that. Eventually this trace disappeared as well and never re-appeared. So about two years after the trace, if there was one, had disappeared I turned the denitrator off. There continued to be no trace whatsoever of nitrate and the denitrator has remained off.

If there was nitrate present and it had disappeared then routine seawater changes wouldn’t have been the cause as these have been done bi-weekly ever since the aquarium started (though at first they were weekly). It wasn’t the denitrator as this was turned off and nothing re-appeared. I assumed that bacteria had colonized the very porous reef rocks and these were dealing with any nitrate, as well as ammonia and nitrite. I decided to remove the bio media from one of the canisters. It didn’t happen.

The canisters, both of them, were left running in full bio-mode as I didn’t do anything because of the reef, it was so successful and natural looking that I was afraid that if I made a mistake the livestock would suffer and I wouldn’t have time to generate a new bacteria population. After a while, I thought that this was ridiculous – and it was as there are two canisters and they both have the capacity to bio-filter the aquarium. So I removed the media from one, then started it up again empty as it is used for surface agitation.

To date, six months down the line, there hasn’t been a problem. So now I’m thinking I’ll remove the bio-media from the other canister. Going on previous performance it’ll be a while before anything is done! I feel certain that there isn’t a need for bio-filtration with the canisters any more.

When I removed the bio-media I expected that there would be visible life within it (Eheim sintered glass). There wasn’t, none at all, at least any I noticed. The aquarium is full of life, mobile and otherwise, so this was a surprise. On cleaning mechanical media I am always rescuing tiny shrimps.

I was really pleased with the state of the bio-media. When washed only a very small dusting of dirt appeared, one rinse and it was gone. This was down to the four weekly mechanical media cleaning, also the mechanical media set-up. The entire mechanical media was before the bio-media, taking the form of a coarse sponge, a very fine filter ‘cloth’ one half inch thick and another fine sponge, so the filter ‘cloth’ was sandwiched tightly between the sponges. It clearly worked.

During the operation on the canister I noticed a fair growth of some toadstools in one area on the reef. All the corals grow at a quite fast rate and the toadstools are the fastest. So out came the sharp scissors and off came their heads. Very drastic sounding but it has been done several times before without mishap. They grow back rapidly.

Toadstool Coral

I also noticed more new corals growing beneath, toadstools again, six in all. Four were removed entirely and two left. The photo (sorry, it isn’t particularly good) shows the cut ‘stalks’ and also the two small new ones that were left.

The cut corals look awful at first but they don’t stay that way for long. First polyps re-grow, then the heads start to increase horizontally and the stalks lengthen.

It’s all quite miraculous really.


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