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Current Setup: 90 Gallon with 2 fish, 8" P. loiselli (male), 6" P. loisellei (female).

I noticed these tiny bugs in the tank a few months ago. Didnt think much of it at the time, they werent latching on to the fish, or seem to be doing any harm, so I let them be. Now they've multiplied! An infestation of epic proportions!!!

Best I can describe them: most are small--like specs of dust. The larger ones are about a half millimeter in diameter-- round or football shaped. Under a normal magnifying glass, with my face pinned against aquarium, I can almost make out what seem to be antennae on their head or front end (the direction they're moving). They crawl on every surface, and can swim--but awkwardly. Viewing them inside the tank they are light yellow/light-brown in color.
When they are siphoned into a white bucket I use for water changes they take on a dark, almost black color.

After doing the Google search, the closest possible match I've found so far is DAPHNIA. If that's what they indeed are, is there any action I should take? I've read that many fish would eat the Daphnia. Although, my loisellei would probably eat those fish.

My dilemma: are they a pest, or could they be beneficial?

My solution would be take a sample to a good LFS to check out exactly what it could be.

You might even have to go to several LFS to find an answer.

Have a look in [link=My Profile]http://
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Keith

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Let's see. Brown, about half a millimetre in size, prefere to crawl on surfaces than swim, and multiply at an alarming rate?

You have Ostracods.

Ostracods are aquatic crustaceans with a hard outer shell (and are only very distantly related to Daphnia, which always swim and never crawl on surfaces). The small size is why your big Cichlids are ignoring them - Parachromis loisellei, particularly specimens the size of yours, are looking at much bigger prey than Ostracods to satisfy their hunger. Though if your loisellei pair breed, the fry will have a nice time hunting the ostracods. How effectively they will deal with the ostracods is a moot point though, as quite a few fishes that would otherwise seem well adapted to devour them leave them alone. Probably because they have the ability to lock themselves down onto a surface, barnacle style, and make themselves impervious to attack from all except the very well equipped and the very determined.

Go take a look at some ostracods at this website.

Ostracods can be found in both freshwater and marine habitats practically worldwide (chances are there are even polar species in existence), and as that page says, there are even terrestrial species to be found in suitably damp environments (a bit like the way woodlice have evolved to be land living crustaceans while the rest have stayed in aquatic environments). The typical ostracod has several pairs of legs which can be withdrawn completely into the carapace for defence if need be, and is a complex segmented animal with a very effective outer shell.

Here is another page devoted to ostracods. they have a fairly long lineage, and as a result, are used as one of the 'key animals' for dating certain geological strata, as the appearance of certain species and body forms correlates very tightly to geological time scales, so that, for example, Jurassic era ostracods will be noticeably different from Triassic or Cretaceous ostracods. Nice of them to evolve like that in accordance with our labelling scheme for geological time - a happy coincidence!

If your loisellei pair breed, the fry will probably have a good go at hunting them, but may find them difficult to deal with.

The only problem they will cause the average aquarist is one of presenting an unsightly infestation if their numbers explode. Which probably means you're overfeeding your Cichlids a bit, and these critters are feeding on the leftovers because there's nothing else in the tank to do so.

Hope this helps!


Panda Catfish fan and keeper/breeder since Christmas 2002

Ostracods...
thanks for the info. Some of the pictures lead me to believe they could possibly be Ostracods. Although I wont know for certain unless I have a sample put under a microscope.

In any case, Daphnia or Ostracods... what should I do about them?
Im gonna try to cut back on feedings for the fish, and possibly keep the infestation of the critters in check by doing more water-change/gravel vacs. Any other advice is greatly appreciated.

Wow! I believe my 5-gallon hex also has these little critters. They are everywhere, and I don't think I'll be able to get rid of them unless I totally strip down the tank and start from scratch.

I am sorry for the semi-hijack, but thank you for the information. I have been trying to figure out those little guys for a couple of months.

Dave

Actually, I've had them in the past.

I didn't need a strip down to get rid of them. I just fed less food to the fishes. Eventually, the ostracods ran out of food that wasn't being eaten by the fishes (plus they were out-competed by the Malaysian Livebearing Snails that I had at the time when I reduced my food input) and they just, well, packed up their bags and disappeared.

Ostracods are actually little scavengers by nature - detritus feeders that pick through the mulm for any tasty titbits they can find. If there's a food source in your aquarium and you accidentally introduce them by some means (transferring a piece of bogwood from one aquarium to another is a favourite means of transmission, as they seem to like living on bogwood) then they'll exploit it and hey presto, population increases. However, if there's enough competition for food in there, they tend to lose out to bigger mouths such as snails and fish.


Panda Catfish fan and keeper/breeder since Christmas 2002