Old Tank Syndrome? How to combat it?

[LedZep fan2]

Hey everyone, hope everyone had a good Thanksgiving!

Well I think my tank has hit the wall with the 2-3'' sand bed. The tank is going on 7 years and I've begun to have a cyano/algae problem. I don't overfeed (only every other day) and there are only 7 fish in the tank (Purple tang, mutlicolor angel, coral beauty angel, blue spotted jawfish, and a pair of true percs). Throughout the 7 years I have not really touched the sand bed due to the fear of initiating a hard cycle. The only things that do are the bristle worms, pods, and nassauria snails.

My question is, how should I go about battling the old tank syndrome? My plan was to take regions of the sand out over the course of a month or two, rinse them well with water to remove the detritus then add it back the same day. Does this sound feasible? I also wanted to add a few powerheads in order to avoid detritus build up. Another idea was to get a sand sifting goby and attach a sock in my sump to pick up any of the crud kicked up by the sand sifting goby. My only concern would be any issues between the goby and the jawfish. Any thoughts?

Thanks for all the advice and happy holidays!

[bertoni]

If I went to the trouble of removing the sand from the tank, I would ditch it at this point. Replacing it is fairly inexpensive, and rinsing it won't remove any adsorbed phosphate. I probably would try running some GFO and maybe tuning the skimmer before going to the effort of replacing the sand.

[dkeller_nc]

If you mean "old tank syndrome" in the traditional sense of the word to mean elevated nitrate levels, read up on carbon dosing. A sand bed in and of itself doesn't necessarily equal a problem, even a quite old one. My 20 gallon nano has been running since 2004, with the original 2" sand bed, and with no maintenance done to it, such as "gravel vacuuming". Despite this, nitrates in this tank are undetectable, and phosphates consistently less than 0.05 ppm.

The tanks is heavily stocked with corals, and gets nightly additions of phytoplankton and zooplankton.

I attribute the low nutrient levels to carbon dosing (in this case, with vinegar), GFO use, and heavy skimming.

But yeah, if you're going to go to the trouble of removing some/all of the sand bed, I agree that I wouldn't re-use it. If the tank's been running for years with high phosphate levels, then you'll have to use an awful lot of GFO to get it to re-dissolve in the tank water and be removed, and it's a heck of a lot cheaper to buy more aragonite sand than to buy a lot of GFO.

If you really, really want to re-use the sand, though, I would acid wash it. A day or two in straight vinegar or 0.1N hydrochloric acid would do the trick.