I have a 125 that is infested with Isopods.There is a Dresser Crab in there too.I need better filtration so for now im not adding anything.How do I rid my tank of these things?I know there are several types of these and some are carnivoris.They are eating algae as I can see it in their bodys.They are clear and shaped like a comman roach.Gross!Any advise?TY
Leave them alone.... they will burn themselves out some in time.
The parasitic ones are not as commonly seen... especially not in plague porportions, but keep an eye out for them... they are larger and have these mean eyes... reminds me of a angry baby seal.
This is your common herbivorous munnid isopod. Seen running around all over the glass. I really need to get a size comparison shot... they really are quite small.
This is another gentle isopod is the sphaeroma that looks very similar to the parasitic cirolanid but are very distinguihable when you know what to look for. They are also called a Roly Poly and I will show you a pic on how they got that name. They are quite large in size and it actually surprised me when I saw them for the first time.
So, you find a large pod... the first thing to look for is if some of them have what looks to be a claw on their.... well.... backside. These are the males. Right away you can set your self at ease that they are not parasitic. For if your population has one of these the chances are the whole batch is of the same critter.
Here's the male.
The female lacks this appendage.
The eyes are also a dead give away. The parasitic cirolanid have large eyes towards the front and they are very mean looking. I always say they remind me of a mean baby seal.
Look at the eyes on the female. They don't look "mean" and they are on the side. I will try to make a comparison shot of that.
If you can catch one, grab it and take it out of the tank. It may roll up in a ball immediately... if it doesn't, poke it a few time with something and it should proceed to roll. This is very distinctive of the sphaeroma and looks something like this...
And just to throw it in .... here's a side view of the male.
Renee's correct. the pods will either wax and wane with available food, or will give way to Gammarids and/or Mysids (which both feed on the isopods). either way, they're a sign of a healthy tank, and will provide additional food for many fish.
im sry but im not a big fan of worms, pods .... they just look scary to me..
Ryan, if ya wanna enjoy this hobby ya better try to get a little bit of awe for these critters. You'll drive yourself nuts trying to get rid of them and your tank will suffer your attempts. You may not be a fan of them but your tank is a HUGE fan and will greatly benefit from the biodiversity. Read about them and watch them... you'll grow to love them..... try at least before you start to "remove".
Not to mention...if someone was hell bent against...well, trees for instance... and decided to start wiping them out.. the kind of chain reaction it would have on the environment.
Basically, your tank is a mini eco system. Now, you can keep the beneficial "bugs" in there, that will feed your fish, eat fish poop etc. or you can wipe them out. (I could tell you exactly how to do that...but I will not). If you wipe them out, that "niche" WILL be filled by another life form and that second "tennant" may not be as friendly.
A real example of this just happened to me this past Summer. I have TONS of chipmunks in my yard. I wanted them gone. They ate from my garden, they made holes everywhere. So... I did many things, and yes, reduced the population. However, I then had LOTS of problems with German Yellow Jacket wasps, and black water snakes, who, in turn, took up residence in their dens. I was better off with the cute lil' chipmunks.
I dunno...I may be one of those werido's but... yeah... that tang.. it's purdy... but that corner...filled with the swarm of bugs..and the wormies poking out...THAT has got my interest.
From your description it sounds like you have Sphaeromatid isopods (pictures provided by seahorsedreams above). Cirolanid isopods can be predatory or parasitic, but will not eat algae, so you should be in the clear. Unless you see some of them attached to your fish, then you probably just have a population of Sphaeromatids.
Their population will probably wax and wane and some other tank inhabitants may eat them. Sphaeromatid isopods are generally considered a beneficial inhabitant and we should do everything we can to encourage beneficial inhabitants as it makes the already weak food web in our tanks stronger.
I have a decor crab thats all,Every one else is in the 75 im scared to put them back.Ther are hundreds mabe a thousand.The aquarium they are in is a 125.
We all like to say Wax and Wane alot don't we! I really can't add anything, I would never touch a beneficial pod population. I've had them cover a glass panel. I love my pods.
Am I the only one who finds is funny how many of us spend all these multiple thousands of dollars on our tanks, only to be most amazed by the "free" creatures that are inherint with having a reef tank.
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isopods 
ryan 
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My seahorses love them.