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how long have you been able to keep a sea hare in your tank?

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i have bought two sea hares over the past month. both have died within a week. they definitely do a good job of eating my hair algae, but i have been extremely unsuccessful in keeping it alive.


i have a 24g with a decent sized frogspawn and i think the last one got stung by it...


i think im done with sea hares.i heard they are toxic as well. so far nothing has gone wrong with my tank,no spikes in nitrates (but to be safe i have definitely done water changes after each one died).


any one have any suggestions for the long haired algae in my tank? i know tangs eat algae, but id rather not put one in my tank.

Edited by yaridong

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I am a licensed fortune teller, with authority bestowed upon me by the council of common sense. I have seen the future of this thread and it is bleak. Every question you are about to ask has been asked a thousand times this month, and anybody worth their salt is annoyed by your disregard for the search function. The only replies you will get are worthless conjecture and anecdotes.

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3.5 months in my tank....and still alive and healthy when I took him back to my LFS where he lived happily for another month before being sold again.

My guess is you don't have enough to feed them and/or you are having salinity, temp, alk swings, current too strong. They seem to be more sensitive than any other invert I have had before.

My one sea hare was able to easily eat a 3" x 4" piece of seaweed a day and he was on the smaller side. They have a voracious appetite and unless you tank is packed with GHA they will need additional food. The only reason I got rid of mine was because I was not able to feed him consistently every day (work and travel) and they are pooping machines.

They are not toxic (this is a bad myth about them)......but left for dead just as anything else in your tank will cause issues.


As far as the GHA….

Phosphate reactor

Look at the age of your lights

Length of light cycle

How much and how often you feed the tank

Up the water changes

Look at the quality of water for your water changes

Manually pull out as much as you can

Mechanical filtration….filter floss, filter sock, etc

Time……will not go away over night

Edited by jfarabaugh

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Builder Anthony

Sea slugs have a short live span with most not living for more then 3 months.



Edited by Builder Anthony

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Fix the GHA problem. Don't put an animal band-aid over it.

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I have 4 sea hares right now.

1 was loaned to another member here who never returned it and has since purchased it for his deposit price.

1 was loaned to two other members here and has been returned each time and is currently in my tank and eats nori.

The other 2 are being used to rent out to folks on CL, cost is $5 and a $20 deposit refunded on live return.


They have all been traveling around and dumped into various tanks with obviously poor water quality(hence the hair algea and need for something to eat it) and I have not lost one.

Tho maybe the reason my original one was never returned was cause it died, I dont know.

But out of my 3 remaining ones, they are still alive and munching HA, and each has been in at least 4 different tanks in the last month(not including my tank, so 5 total)


I have no HA in my tank, and have gotten this one to eat the nori from chinese food markets.

Im sure when it gets picked up on the weekend, it will be happy to eat some yummy HA again.


I think they are collected in the wild in large congregations at mating time which is close the end end of their life cycles(from my understanding), which may explain their short-liveness in our tanks.

Like I said tho, I havent personaly lost one and its been around a month of them all making the rounds to various tanks, a very stressful situation for any animal.


I think sea hares are an awesome creature and very useful.

I recommend the standard old-school float-bag-add-water method of acclimation to people who use my sea hares.


They have very specific feeding habits, and Im surprised mine is eating the nori, but it seems to sustain it between rentals.

I dont know how the nori would work long-term, but for now its all good, it loves it and climbs the glass to get to the clip.



Let me also add the that a sea hare will NOT fix your problem, but it is a way to remove the HA that is already their without adding a hard to catch fish that will increase bioload and that may or may not eat the HA, only reduction of nutrients(especially phosphates) will prevent more HA from growing.

Edited by CoralWhisperer

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one month :(

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one month :(

why? this thread is 4 years old lolol

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I know this is an old thread but 2 years I got it small and it took care of a 250 gallon system for its life also ate bryopsis and cyno they die right after breeding and if you get them young they live a long time as long as they have food it was about 15inches long and weighed over 1 lbs we it died of old age was so used to me moving from display to fuge  all I had to do was lay my hand flat and it climbed right on to be transfered

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Ive had mine for 5mths

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