Pete Giwojna

Dear Sean:

No problem, sir — keep the questions coming!

Well, I certainly can understand why the guys at your LFS gave you the advice they did, and in general, their suggestions are quite sound. A 49-gallon aquarium loaded with live rock has all of the biological filtration it should ever need without any help from the canister filter, so it is certainly understandable that they recommended removing all of the bio rings and replacing them with nitrate remover. They would have expected that the live rock could pick up the slack in terms of the biofiltration, and that making this change would help keep the nitrate levels in the aquarium nice and low.

Likewise, activated carbon does a wonderful job of removing organic pollutants from the aquarium via the processes of absorption, adsorption, and chemisorption, but the rate that sorption occurs slows down over time so that the activated carbon needs to be changed regularly for best results. Switching out the activated carbon after 10 weeks is not unreasonable under normal aquarium usage, but probably a little premature in your case since the carbon had only been used in a new aquarium with a very light bioload. But changing out the activated carbon periodically is a very sensible, and I can’t fault them for their recommendation in that regard.

And it’s always advisable to rinse and clean the prefilter sponges regularly. So I don’t really have a problem with any of their advice per se, but the timing for replacing the filter media was certainly unfortunate. In the 10 weeks the aquarium had been running, a sizable population of beneficial nitrifying bacteria had populated the bio rings as well as the porous activated carbon, so removing all of the bio rings and all four packs of activated carbon in one fell swoop no doubt diminished the biological filtration ability of your aquarium significantly, and I would not have replaced them right when you were beginning to stock the aquarium and increasing the bioload.

In short, there was nothing wrong with that changes your LFS recommended — they just picked the worst possible time to replace the activated carbon and remove the bio rings. (If it’s any consolation, I would not have anticipated any sort of an ammonia spike in a 49-gallon aquarium with all that live rock despite removing the filtration media from the canister filter a little prematurely.)

I would have left everything in place for the first few weeks after you added the seahorses to help the new aquarium adjust to the heavier bioload, and then gradually replaced the activated carbon, changing out one bag each week for the next month.

If I wanted to remove the bio rings, I would again have waited several weeks for the system to stabilize at the heavier bioload before I replaced any of them, and then gradually phased the bio rings out, removing no more than one tray of bio rings at a time.

I would keep the four trays of activated carbon in your canister filter. Use a good brand of activated carbon that’s low in ash and free of phosphates, and be sure to replace the activated carbon one tray at a time on a regular basis.

If you want to include some of the bio rings to provide supplemental biological filtration, that’s fine. In that case, I would remove the water polisher pads and include two trays of bio rings along with two trays of the nitrate remover.

It shouldn’t take anywhere near eight weeks for your main tank to adjust to the higher bioload because of the live rock and live sand, but any new bio rings will require at least two or three weeks to build up enough anaerobic Nitrosomonas and Nitrobacter bacteria before they can be of much help in the process.

Best of luck getting the ammonia levels in your main tank back down to zero again, Sean! You did great to have a fully cycled quarantine tank, complete with a protein skimmer, ready and waiting in case it was needed. Well done, sir!

Pete Giwojna

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