Astraea Snails Make Short Work of Algae

Astraea snail chowing down on nuisance algae

Astraea snail chowing down on nuisance algae

This past year, I rediscovered how great an army of snails can be. At Tidal Gardens, we go pretty light on cleanup crews in general. For example, there really aren’t any hermit crabs to speak of in our systems. In 5,000 gallons of reef tanks, there may be only one or two hermit crabs. Most likely they arrived as refugees from local customers taking their tanks down who needed to re-home some of their inhabitants. I am not a fan of crabs because there is always a risk they might kill something they should not be killing, like another member of the cleanup crew or a coral. Long story short, I don’t trust them.

I don’t have the same level of distrust for snails. However, what tends to happen is I order a large quantity and over the years they dwindle in number and I forget all about them.

A little while back, we had a system that really struggled with algae. This tends to happen towards the middle of summer as the nutrients that build up over the winter without any problem suddenly get a whole lot more light. That causes algae to grow if we don’t ramp up water changes heavily. This past summer, we didn’t do enough water changes, so we got some nuisance algae.

At one point, a couple of the tanks looked unrecoverable. We were scrubbing the tank and trying to clean the individual corals for a while, but the algae was just too persistent. Once algae starts growing on the corals themselves, it is very difficult to manage.

Astraea snails do an amazing job of cleaning up nuisance algae

Astraea snails do an amazing job of cleaning up nuisance algae

Instead of just restarting the tank, I decided to put in a bunch of Astraea snails, and the results were nothing short of miraculous. It didn’t even take a week for them to do serious work on the algae. One system that seemed like a lost cause because of the algae completely recovered. The snails did an amazing job of eating the algae around each polyp of coral, and the system now looks pristine.

There are a couple things that make these guys great herbivores. First off, they are fairly small. There are certainly larger snails you can get, like Mexican Turbo snails for example, but there is an advantage to snails being smaller. Smaller snails don’t bulldoze your tank and knock corals all over the place. Also, smaller snails can get into smaller crevices to clean out algae that larger snails won’t be able to reach.

Second, they are surgical when it comes to cleaning. As I mentioned, we had algae practically growing on the corals themselves, and these snails ate right up to the edge of the polyp. They literally made what looked like an unrecoverable system spotless, and that includes the corals.

Third and perhaps best of all, they are cheap. You can usually find them for around a dollar a piece.

No cleanup crew member is perfect, however. The main concern with these snails is they struggle a little bit flipping themselves over. I don’t know how some of these snails make it in the wild, but for whatever reason, if you see one flipped on its back, don’t assume it will be fine. Give it a hand and turn it upright.

The second thing is, some of them come with their own pests in the form of pyramid snails. Pyramid snails are tiny, so it may take a close look to even notice them in the first place. These small cone-shaped snails will eventually kill their host, so I recommend physically removing them whenever you see them. Astraea snails are pretty tough, but the bigger concern is that pyramid snails can move on to other mollusks in your tank, like, say, that $200 clam you have as a centerpiece. I try to remove them manually if ever I spot them.

Pyramid snails (indicated by the red arrows) are pests often found on Astraea snails

Pyramid snails (indicated by the red arrows) are pests often found on Astraea snails

Third, check to make sure the snails come from a tropical climate. The ones we have are from Florida, which is great. Unfortunately, many types of snails that are sold in the hobby are harvested from cold-water areas, some of which look a lot like Astraea spp. Cold-water snails do not last long in our tropical aquariums.

The last point is to take your time acclimating them because snails handle the acclimation process somewhat poorly. Drip acclimation works best. Also, be sure not to subject any inverts, like snails, shrimp, clams, or worms, to coral pest-control dips. It may seem to go without saying to avoid these dips, but trust me, it’s been done before by many hobbyists, resulting in the quick demise of the poor inverts.

In conclusion, I wanted to share my overwhelmingly positive experience with these snails. They are making a world of difference in the tanks here at Tidal Gardens. They are so easy to overlook, but these snails literally saved us the hassle of restarting a couple large systems.

Photo and video credit: Than Thein

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About Than Thein

Than Thein is the owner of Tidal Gardens and Advanced Reef Aquarium. Than's love for all things underwater began early on when dogs and cats were strictly off limits, but a fish tank? Sure! What started with a 10-gallon goldfish tank eventually turned into a 5,000-gallon greenhouse coral propagation system. In addition to coral aquaculture, Than's other hobbies include scuba diving and underwater photography and videography.


  1. Margo Love says:

    How do Astraea snails fair in the same taml with a large lunar wrasse, (about 6″ long) ?

    Thank you,

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