The humble ugly algae eating machine. The Sea Hare.

Heres the deal -- the sea hare is a member of cleanup crew member -- only really talked about as a last resort.
Difficult to keep alive -- but with a worthy reputation.

Sea Hare, Dolabella auricularia. © Mila Zinkova (wikipedia.com)

I have a closed loop system. As such I rely on my live rock filtration to do my managing of nasties and goodies in my tank. Recently a spate of careful albeit live food feeding to my corals (don’t do fish) caused PO4 spike that threw my tank out of balance. You know the story, a moment in the tank, a lifetime in the water.

So I started to get very bad hair algae -- for the life of me I couldn’t get rid of it. Tried the usual methods -- filtration -- PO4 remover -- more regular water changes -- dosing liquid po4 remover. My problems were exaggerated because I run a very stealth Zen like approach to tank keeping. No skimming or reactors -- just my external canister filter with 3kg of broken reef plate in the filter trays.

I’d read about Sea Hare’s -- natures voracious eaters of green algae -- in particular hair algae. I had a lot of hair algae, my theme tune was ‘ the hills are alive with …’ you get my point…

Sea hares -- are secretive, ugly, slow moving, gentle, alien, not toilet trained, active sleepy, acrobatic, dull beasts. I purchased my fairly large sea hare from my LFS.

I’d read that sea hare’s are particularly sensitive to introduction into a new tank. In the past I have ignored this and been bitten -- so in this case I was careful. I dripped the beasty in over 4 hrs -- excessive I know -- but I had a higher salinity in my tank to shop so was being extra careful.

The sea hare -- dull grey in its pattern -- lump like -- and soft spiky appendages all over. It has a head with a mouth -- two simplistic eye stalks -- and in’y and out’y hole  (more on that later). As soon as I was ready I gently drifted the sea hare out of the bag into the corner I had ear marked for it. Main lights were on -- I had read it was more a night time beasty so expected it to be in light shock and tank shock and hide in the corner until night time. NOT a BIT OF THAT!

I kid you not -- as soon as the sea hare gently rocked down to the corner -- its mouth had already started pulling in hair algae. From the moment -- no repositioning -- not pause -- straight out with the head and puling in hair algae in front of me. I realised that the poor thing must have been really hungry. Within an hour it had cleaned the corner it had started in. It then, slug like, started to move around from where it was -- slowly stretching its body out to other parts of the rock near it.

Over the course of the afternoon and into evening its didn’t stop eating. It mooched around in the corner for a while where it started but soon started off towards the glass. Most importantly I noticed its soft mouth rasping against the glass. I watched as it like a giant gravity defying slug -- pushed itself up the glass towards the top of the tank. Its head coming out of the water surface (the lights were still on and it didn’t care)
It was trying to reach the very top of the tank as if to check its eating boundaries!

Now I noticed its out’y hole -- mid way up its body -- towards the thicker end away from its head -- from it a line of browny flaky pellet shaped poo started to come out. I then realised it had left lots of these little packages where it had started. Sea hare poo! So not only had it not stopped eating -- it had digested the hair algae almost instantly into neat brown packages.

So off to bed -- and wonder and worry. But cest la vie attitude -- what would it do tonight -- would it do the whole tank in one night at this rate? Would it knock things off?

Sunday morning I wake up and check -- the tank hasn’t been completely house cleaned of algae. Sea hare is snoozing in corner right at bottom of tank.
Rock is looking picked clean in parts.

Over the course of Sunday it followed this pattern which it still does now -- sleeping until about 2pm and then mooch around and eat. I noticed Sunday night that it was near some corals -- and so watched what it did. It munched up to the coral -- around the coral -- on the coral -- and not once did it knock it off or move it. I realised it was a gentle giant -- and very delicate and precise about where it ate -- it targeted only the hair algae by spotting it first not just grazing the whole area. When it needed to get to something it would normally elongate its body and stretch to it -- or stretch over or squeeze into it (its body of course is just water really).

Within the next week or so -- it slowly moved around the tank and only twice knocked over corals that weren’t fixed down (none of my corals are) but these were especially loose as they perched on some of my live rock. It also did acrobatics moving around the tank glass when lights out -- either at the top by water line or mid way -- stuck to the glass ‘anti gravity’ like. When it ran out of stuff at water line it would do a gentle ‘drop and roll’ and fall from the glass onto the sand.

In my time with it I’ve grown to really find it very alienly cute. Hard worker -- never talking back just a bit filthy with all the poo’ing.

I would recommend a sea hare whole heartedly -- the best way is to share someone else’s Sea hares are very cheap, £9 (14USD) for my large one. But once you have given it a home the worry is it running out of algae and starving. So you can take it back to LFS -- and they may be in the same problem as you after having it back for a while. As you can tell mine was very hungry when I got it. Or you can try and keep it alive with nori sheets or other algae. Or you can borrow one from someone nearby or local fish club or forum ! Like this one.

I’m going to try and keep it alive and then if I have to give it back to the LFS. I’ve grown quite attached to it.

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Ed note: We collected a few videos of sea hare’s in action, enjoy.

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Have you tried a sea hare in your nano before? What are your thoughts on using a Sea Hare for algae control? Express yourself in the comments section below.