Jumping to conclusions?

[Lynnzer]

For the last few weeks I have suffered occasional losses of Chili Rasboras and CPD's. From time to time I have found a floater and despite the water showing nil on Ammonia, Nitrites and Nitrates, and also with frequent water changes they still go to fish heaven one by one.
There's no mass deaths. There are no signs of illness at all and even no fish showing peculiar behaviour to make it appear to be anything to do with their environment. So I've been scratching my head on this one.
Last week I took a breeding pair of endlers and placed them in a tank, around 10ltrs, which has been running properly cycled for a good month or so. It was even using a filter that had been in use for months too so it worked straight away.
Anyway, the endlers seemed OK. The female is gravid so I'm hoping for offspring.
Then yesterday I took out some small water lettuce from one of my larger tanks and put into the small one.
Today the male endler is dead. The water still tests zero on all counts.
Now, and the title says it all really, since the deaths of the chili's and cpd's were taking place in the tank with the main spread of water lettuce is it possible that this could be problematic? I have read somewhere that water lettuce is poisonous, yet somewhere else says that it's a food source for some people. What poison does it have even? And is it released when, for instance, a leaf goes to sludge as they sometimes do.
I can see many reports of it being a great plant with long trailing roots that are great for small fish. However is it really poisonous to the extent that it may have detrimental effects on nano fish?
It's strange that it doesn't seem to affect any of my larger fish, even neon tetras and Ember tetras.
Personally I do like them as they are truly lovely to see floating on top with the maze of roots trailing below.

 

[Colin_T]

Pictures and video of the fish?

What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).

I have never heard of Water lettuce being poisonous. There are plenty of animals in the Amazon that eat it and heaps of people keep it in ponds and aquariums. Koi and goldfish eat it so I doubt it is poisonous.

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I would say there is either a disease (maybe velvet) or a water chemistry issue, or a possible poison/ contamination in the water.

You can check the fish for velvet by shining a torch (flashlight for the US members) on the fish at night, or by taking a picture of them using a digital camera with the flash on. If there is a yellow or gold sheen over part or all of the body and the fish isn't meant to be yellow, then they have velvet. Velvet usually causes the fish to rub on objects but not always.

Water chemistry (pH, GH & KH) maybe incorrect for the species you have.

Sometimes fish (usually newly imported ones) can have trouble adapting to new water and die after you do a water change or just die for no apparent reason. This is normally caused by the fish going into a tank that has quite different water to where they came from. This can be pH, GH & KH, but can also be caused by the stress of being shipped around the world and put into a range of new water in a short period of time. It regularly happens to rummynose tetras and some of the other less common tetras. If this is the case, the best thing to do is stop doing water changes for a couple of weeks, and then start doing small 10% water changes once or twice a week. Gradually build up the percentage changed over a course of months after the fish have recovered from the stress of being shipped around the world.

 

[seangee]

What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).

Important questions. Chili rasbora thrive in soft acidic water. Mine are in a tank with 0KH and GH and the pH is <5, possibly well below as I have no way of measuring that low. CPD are more tolerant but mine thrive in a tank where the pH is slightly below 7 with dGH = 6 and dKH = 3. I would not try to keep endlers in either of these tanks because they would live very short and unhealthy lives. Conversely these 2 species would not live very long in a tank that was perfect for endlers.

No point in trying to guess until you can respond to Colin's post - but it is worth mentioning that newly purchased CPD have a very high mortality rate, when I bought mine I insisted the store kept them for a month in their tanks. I reserved their entire shipment (50+) but when I went to collect there were less than half of that. But no further losses and the school is still self sustaining 4 years on.

 

[Lynnzer]

It could be the mortalities are down to newish fish though most have been with me a few weeks now.
I'm stuck with the GH right now though as I'm out of bottle no2 in the GH test kit. I won't be buying any more from NT Labs though as I think they are damn inconsiderate. The GH test has to be done from 2 bottles. The first one needs 2 drips in a 5ml water sample, then we are supposed to just keep dripping away with bottle no.2 until the sample turns yellow. In my case it's around 22 drips later. You can almost chew the tapwater, or at least you could but they have a new reservoir they're using now with a pH of 7 and GH of 167. Do you get it though? I mean the drip thing.
What I have now are several bottles of No.1 hardly used, and none of No.2.
I've been told that API has a single bottle test but can I hell find a stockist in this area. I'll be doing an Ebay purchase later today after driving to another fish shop that I thought would have API.
I also sent a complaint email to NT Labs on Thursday or Friday asking them out of the kindness of their heart to sell me some No.2 bottles and ppinting out the anomaly of the 2 bottle test as explained above.
Anyway, apart from the GH, the KH is at just short of 9 drops, ie around 160 pph.
But though the fish mentioned were mostly from a single tank, they haven't solely been. The Endler was in a small tank as a pair.
I'll check the velvet disease when it gets dark but I don't think they are diseased. I could be wrong though.

 

[seangee]

GH and KH are typically tested once as they tend not to change over time. When you keep soft water fish in hard water they eventually die of organ failure (think limescale in the organs). In my own experience fish that typically live 6-8 years died within 12-18 months. As it seems a relatively new tank this is probably not the immediate problem. But I did see in another thread you are using CO2. That would be my primary suspect.

 

[Lynnzer]

Ah, CO2?
Not in the Endler tank. However it's in my TOTM entry and another aquascaped tank but the CO2 is turned off late afternoon and started again early morning. I also have a CO2 checker which is always at green.
However, it's something I'll take note of and will keep it off for a week to see if it makes a difference.
The water does indeed stay the same over the course of time, however the pumping station at the Castle Eden reservoir has suffered a massive electrical problem so they have switched to, I believe, a supply from Keilder which is softer water. That is down by around 280ppm on the GH, almost 2 thirds of what it was.
However that's a new development and wouldn't affect any fish just yet. I've ordered another GH checker and will be able to see what I need to do to rectify any problem if there is one.

 

[StevenF]

From wikipedia

While considered edible, Pistia stratiotes is not palatable as it is rich in calcium oxalate crystals that are bitter in taste. Nevertheless, there are records of the plant being utilized as famine food in India during the Great Famine of 1867-1878.[37]

So wikipedia states water lettuce is not toxic to people but it lasts terrible.

However this site it is listed as toxic if eaten in large quantiies.

As to fish I see anything conclusive with a google search. But a lot of people have it in their tanks. So I would suspect that if it is heathy and growing it probably OK.

The suspect chemical in the plant is Calcium Oxalate which appears soluble in water. Many plants have it some are toxic and some are not. Apparenly some common spices have it. So overall it looks like it isn't toxic.

 

[GaryE]

I would discount fears of water lettuce. It's been a standard for ages.

@Colin_T has the best clue to me. Small rainforest fish, the pattern of deaths ... often that says velvet. It's Ich's less sexy cousin (though not really related) - a parasite known from as long as people have kept fish. It has a special liking for blackwater fish. It's also no fun to eradicate, as the meds that kill it are very harsh on fish too. I know it well as a killie keeper, and am always watching if circumstances make me miss a water change. If I saw the pattern you describe, I would have the flashlight out (I save the torch for the castle walls) and I'd be checking regularly.