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Black marks on sides of tetras
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MissKlaw
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Joined: 23 Sep 2010
Location: Brisbane, Australia

PostPosted: 2010.11.10(Wed)23:58    Post subject: Black marks on sides of tetras Reply with quote

Once again, I've looked through all the info and previous threads, and this thread is the only one that sort of sounds like what's appeared on my fish but with no replies plus I don't have black algae spots appearing anywhere in my tank, just a small amount of diatoms which are almost under control following a boom in snail numbers and addition of fertilisers.

Two of my rummy-nose tetras have black marks appearing on their sides, not raised - it almost looks like someone's smudged them with a bit of charcoal. There's been no change in appetite or behaviour, no flashing or anything, I'm just wondering if this is something I should worry about.

This first image is better (in terms of seeing the positions of marks, not quality), but I included the second as well since it has both fish in question in it.




Tank:
- 50L, with 20W light and bioball/Purigen/ceramic noodle filtration, 20% water change weekly
- Fine gravel substrate, two pieces of driftwood, banana lily + crpyt (unsure which type) + anubias (again, unsure) + much-trimmed-back lace fern & wisteria, two fake plants
- two panda corys, two peppered corys, six rummy-nose tetras, eleven neon tetras, and one lonely cherry barb I felt sorry for, plus an unknown number of what I'm guessing are pond snails (came in on live plants)
- pH hovering between 6.8-7.0, NH3 0ppm, NO2 0ppm, NO3 21ppm
- Temp is 27-28 degC
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deborah_claro
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Joined: 11 May 2006
Location: Virginia, USA

PostPosted: 2010.11.16(Tue)10:26    Post subject: Reply with quote

Hi. From what you write this doesn't seem like either a disease or a disaster. That's the good news. However, there might be one or two things you could do to improve the conditions in the tank.

First, the black marks:
I would not get alarmed over this. If nothing else has transpired since your original post, and if the fish seem healthy and active, then I'm going to say that the black smudging might be from one of two causes:
1. the fish is darkening due to being over a light colored substrate, or
2. perhaps some of the reflective material is missing from the scales of these fish. That would cause some dark color to show through.

A similar thing happened in one of my tanks. A couple of my lemon tetras (Hyphessobrycon pulchripinnis) developed small dark spots on their flanks about a year and a half ago. It does not seem related to anything sinister at all. They are perfectly healthy and are the two most dominant fish in the group. In fact, I think the coloration is linked to the domination. I do have light colored sand in that tank.

From the photos, your rummynose appear to Hemigrammus bleheri. (Because they lack the mid-body line and don't appear to have a black edge where the anal fin meets the body.) If so, in H. bleheri, the red nose should be extending past the gill cover. Optimal water conditions will encourage this coloration.

In my opinion, your nitrates are a bit high for this fish to feel really comfortable, which is why we are not seeing the full potential of the red nose. I'm surprised your plants aren't taking up those extra nitrates but, as they aren't, you should be doing larger water changes.

A partial water change of 20% weekly isn't enough, IMO. That's a small tank anyway, so it's easy for the water quality to go off in a hurry. I think it will continue to deteriorate if you don't do larger water changes. I suggest you move to 25% and replace the fake plants with real. That will help keep the nitrates lower (aim for 10 ppm) and keep the water cleaner.

Otherwise, things sound good. 20W of lighting over 50L (approximately 13 gallons) seems fine, and the pH is good. Why don't you try these couple of changes and let us know how things go?

Deborah
Very Happy
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MissKlaw
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Joined: 23 Sep 2010
Location: Brisbane, Australia

PostPosted: 2010.11.16(Tue)20:33    Post subject: Reply with quote

I'm in the process of working out a new, more heavily planted arrangement and where I can order the plants from, so hopefully that'll be done in the next couple of weeks and will help out with the nitrates. Another person I spoke with suggested it might be a parasite bought in by snails (somewhat rare in aquariums but not impossible) so I've also been removing every snail I spot as a 'just in case'. I'll try doing the larger water changes and see what happens with their colouring, thanks Deborah Smile
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deborah_claro
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Joined: 11 May 2006
Location: Virginia, USA

PostPosted: 2010.11.17(Wed)17:52    Post subject: Reply with quote

MissKlaw wrote:
Another person I spoke with suggested it might be a parasite bought in by snails (somewhat rare in aquariums but not impossible)

This doesn't seem very likely but, as you point out, it is not impossible. It's been at least 17 days since the first post so have you seen any evidence of parasites? Anything protruding through the gills, or emerging through the flanks? Anything untoward coming out of the anus? If possible, should you see such a thing, try to obtain a sample, place it on a slide and take a photo.

Usually other hosts and a whole range of optimum conditions must exist before the life cycle of a snail-hosted fish parasite can complete in the aquarium. However, it's not impossible and you are probably right to remove all the snails. Use medical gloves when handling the snails and either crush them or put them on a paper towel to dry out. Then discard them in the trash.

Deborah
Very Happy
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MissKlaw
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Joined: 23 Sep 2010
Location: Brisbane, Australia

PostPosted: 2010.11.27(Sat)22:59    Post subject: Reply with quote

Well, I still have snails appearing randomly in the tank - not too much I can do about that I guess. Besides which, nothing else is appearing that seems to be parasitic, and it's only the rummy-noses affected, so I think I can safely rule out the snail-borne 'black spot' parasite. And I'm not terribly concerned about the fish at all, they seem just fine.

On a side note, I upped the water change to about 30%, and did a 50% change today, and the rummy-noses' red colour is even deeper than it has been and has 'spread' further back to the gills Very Happy Haven't even done my re-scape/new plants yet, but that's a good start, hehe.
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