Very Strange Creature in My Tank

Hi,I setup my new aquarium 2.5 months ago and I noticed a strange creature 4 weeks ago that looked like a small spider in the gravel. Last night that creature reappeared and is considerably bigger and no one seems to know what it is. I have been losing 1 fish per week, even though testing shows my water to be fine PH 7.2, Ammonia 0, Nitrite 0, Nitrate 40. I have 6 neon tetras, 5 white tip tetras, 1 catfish and 2 guppies. You'll see what plants from the picture. Over the last 4 weeks I have lost 2 gouramis and a few neon tetras. The creature was not seen at all for 4 weeks, it is an inch long now.
Are you able to help?

 

It could possibly be a dragonfly nymph but I'm not positive. The abdomen and legs look like it, but the head/antennae shape seems a little different. If it is, they are predators that will ambush their prey, but I doubt it could have taken out the gouramis. Either way I would definitely try to get it out of your tank next time you see it. You can catch it in a net or shoo it into a cup to remove it.


Your nitrate level is a bit high, as most aquarists prefer less than 20 ppm. While I doubt that was high enough to kill your fish, a water change would be a good idea (and might give you an opportunity to find the little buggy).

 

I would agree that it is a dragonfly nymph. It looks like the two I had in my tank.

I posted a thread about it where someone said they lost all their fish then found a very fat nymph... It has eaten them all.

I suggest removing it from the tank ASAP.xx

 

I agree that it looks like a dragonfly nymph. The thing I also wonder is how he got into your tank? Did you add any plants or rocks that you found in a nearby pond or body of water?

 

When I had mine, everything in the tank was from the LFS so they don't necessarily need to be from ponds

 

I agree that it looks like a dragonfly nymph. The thing I also wonder is how he got into your tank? Did you add any plants or rocks that you found in a nearby pond or body of water?

HI Shayla,
The main rock came from a garden, however I scrubbed it with steel wool before placing in tank. The other rocks came from a hardware store and I washed them. The only way I can think it got in was plants. I bought the plants from an aquarium supply shop, maybe there were eggs on one, or something like that.

 

Sometimes the LFS, when privately owned, has creative ways of acquiring plants. I would be willing to bet money that the store you purchased from did not receive their plant supply from a vendor with a closed, hitchhiker free system.

 

Sometimes the LFS, when privately owned, has creative ways of acquiring plants. I would be willing to bet money that the store you purchased from did not receive their plant supply from a vendor with a closed, hitchhiker free system.

Everything that was in my own tank at the time came from the big brand LFS over here, the plants could come come from a "creative supplier" to the LFS

 

Everything that was in my own tank at the time came from the big brand LFS over here, the plants could come come from a "creative supplier" to the LFS

Also true! I am fortunate enough to have a LFS near me that grows all of their plants submerged in store! I go right up to the tank, point, and take home a healthy plant with minimal melting.

 

Also true! I am fortunate enough to have a LFS near me that grows all of their plants submerged in store! I go right up to the tank, point, and take home a healthy plant with minimal melting.

HI Phisphin,

forgive my ignorance, what is 'melting'? Should the plants be washed under tap water and carefully examined for eggs etc or wash in tank water and examined?

 

Melting is when a plant's leaves disintegrate or melt when switching water conditions. The plant doesn't actually die, but just loses it's leaves and grows back new ones. Some plants like crypts are notorious for melting when switching tanks, while others won't.

I would definitely rinse new plants off and inspect them for hitchhikers, but that really isn't a guarantee that you'll catch everything. It's not uncommon for snails at least to be introduced on plants even if they were inspected, and sometimes more harmful things like the bug you got. Ideally plants should be quarantined like new fish, but in reality a lot of people don't. I guess it comes down to how much you trust your lfs and how paranoid you are about your tanks. You can also do a disinfecting dip in hydrogen peroxide or even bleach, but that's stressful for plants and can do more harm than good.

 

Final update - yes it is definitely a dragonfly nymph and my Wife managed to spot it tonight and I managed to suck it up with my gravel cleaner...;o)

Thank you everyone for your help, much appreciated.

At one point I was starting to think I'd wake up one night and it would be feeding on me!

 

Good you got it.

The day comes I ever spot one of those ugly buggers in my tank. I will tear the tank apart to get him out.

I love dragonflies. But I fins dragonfly nymphs upsetting. Something that looks that just hanging out in the tank. Just...no. Not okay. Haha.

 

Good you got it.

The day comes I ever spot one of those ugly buggers in my tank. I will tear the tank apart to get him out.

I love dragonflies. But I fins dragonfly nymphs upsetting. Something that looks that just hanging out in the tank. Just...no. Not okay. Haha.

Even more upsetting, go to youtube and see what they get up to...... no good. I saw one in particular where the guy had filmed it in slow mo, catching a guppy. Very upsetting.

 

They're so creepy! When I managed to net mine I stood there screaming, not knowing what to do next! Glad you got it!!!x