So. Much. Vacuuming.

[surrendertovoid]

Hello everyone,

I realize that this forum is more for hobbyists, but I don't really know where else to turn.

I recently graduated from college with a degree in marine biology and shortly thereafter was hired to work as an aquarist in a small public aquarium. I've been working there for about a year.

Before working at this aquarium, I never really took care of fish in captivity before. I really love this job and I want to take amazing care of our animals, but I'm not sure if...my organization is doing it right.

Almost all of our tanks are fish only, but we have three small coral tanks (well, small for our aquarium). We have a 250 gallon, a 150 gallon, and a 55 gallon tank.

There is cyanobacteria growing on the gravel (which is relatively coarse crushed coral) in every one of our coral tanks. The senior aquarist tells me we need to vacuum the gravel about three times a week to at least get rid of the cyano (but apparently, doing it every day, but we don't have the time). She told me we take a gravel vacuum, push it all the way down to the bottom of the gravel bed (which is only about two inches deep in each tank), and hold it there for five to ten seconds. We suck out so much water for our tanks when we do this, and it takes forever. We probably do a fifty percent water change three times a week on our coral tanks. And it doesn't seem to help anyway, the cyano comes back in literally an hour or two!

Seeing as I have never taken care of aquariums before, I have been doing a lot of research about how to take care of them, and to my (non?) surprise, I have not found "vacuuming" as a recommendation to getting rid of cyanobacteria. In fact, I haven't read that you should vacuum your gravel anywhere! I've read, in maybe one or two resources, that you should superficially vacuum the gravel to get rid of big chunks of detritus, but that's it.

Are we vacuuming too much?

[SushiGirl]

The biggest thing for cyano is either bad water quality to begin with, lots of detritus (which crushed coral will hold), and old light bulbs. Vacuuming a shallow sand/gravel bed is fine, but I can't imagine having to do it for so many/big tanks. Most hobbyists have deeper sand beds, which you don't vacuum, which is probably why you don't see it recommended much here.

Don't really know what to recommend for you, since you don't own the tanks & it sounds like they wouldn't take your advice anyway...maybe someone else can help.

[SushiGirl]

Hit post once, get 2 posts LOL.

[surrendertovoid]

When we run our water quality tests, everything (ammonia, nitrites, nitrates, and phosphates) always comes up zero (which I've read doesn't necessarily indicate that there are none -- it probably means the cyanobacteria is using it). I don't know how there could be much detritus in the crushed coral, since we vacuum it three times a week.

They might listen to me. It's worth a shot telling them what they're doing wrong. So feel free to advise me anyway! It's important for me to know, so that when I move on to my next job at an aquarium, I won't make the same mistakes there.

[Sk8r]

Two things: nassarius snails (they work UNDER the sand) and turning the lights out. Press the blue number under my blog, go to a post named 'Algae" and read about cyano. Highly curable, but it takes some work, and crushed coral isn't your friend. If you could start a campaign of scooping some out and replacing it with medium grade aragonite you could do a lot, but if you stir up that sandbed much, you're at serious risk of losing a tank.
I don't vacuum at all, period, ever, and have clean sand. Nassarius, fighting conches. Maybe a jawfish or two. And just let them work.

[SushiGirl]

I agree with Sk8r about replacing with sand, but didn't recommend it since it's not your individual tank and that might be a hard sell. We love our fighting conchs.

[dkerns06]

Nassarius snails aren't going to survive long with crushed coral. That's what i(who was ill advised) used to have and every nassarius snail i had died because they couldn't dig in the crushed coral.

Sent from somewhere using something.

[Sk8r]

Dear me. Well, that's going to be a problem. I suggest you sit down with these people and suggest a slow campaign to replace all the crushed coral. It'll be slow, it'll take months to do it safely, but you can put new sand in with an oil (automotive) funnel stuck in a 2" plastic pipe long enough to reach the bottom. Let it pile up. Fish will spread it.
Getting new sand out---net it out. Don't do much at a time.