Friend's tank

[appleblossom]

This is a bit awkward for me as I havnt actually seen the tank, my boyfriend's sister's boyfriend bought a 40 litre 10gallon tank a month or two ago.

He used a sand substrate, an internal filter, and decorated with a peice of coral he got on holiday (possible problem here?? he says he boiled it twice)

He stocked with 2 swordtails and bought test kits on my advice. After a month he was getting readings of nitrate 30, nitrite 0, ammonia 0. I told him he could now add more fish.

over the next few weeks he added 1 betta, 2 shrimp, 2 wagtail platys and a german blue ram.
He also added a borneo or hillstream loach after being told they would take warm water.

After a few days (he doesnt know how many) the borneo loach appears to have died. He didnt notice until his betta died and he found the body of the borneo loach.

Having read that these loaches give off toxins after they die I told him to do a water change. Apparently he changed about 25% and used dechlorinated water.

Over the past week both swordtails, one platy and one shrimp have also died. Having hassled him to give me some water parameters he has tested and got the following:

nitrate 50-100
nitrite - 0
gh - 10-16
kh - 3-6
ph - 8
ammonia - 0.25

I dont know why there is ammonia showing up as teh fish werent added fast and there have only been a few fish left for the past few days so the ammonia surely shouldnt be anywhere over 0 unless the bacteria have been harmed??

other info - apparently when my bloke's sister went round there was a huge algae thing going on and you could hardly see through the tank. She got him to clean it off. After this she pointed out his fish had whitespot - he thought they just had grains of sand stuck to them. He started treating for whitespot at full strength.

Then the sword on the swordtail started to disappear, she told him his fish had finrot, but he couldnt treat for it with the whitespot treatment going on. That fish has since died.


So... any thoughts? My only thoughts are possible toxins from the borneo loach? possible harmful substances in the water some other way? something bad on the coral? bacteria culture damaged (but swordtails i imagine would survive through if the tank cycled again)

 

[Wyld-Fyre]

Once had sand substrate when I had started out early in my fish-keeping hobby. Little did I know, whilst I did my cycling, that there were an ever-growing toxic culture of anaerobic bacteria in the sand. At that time, I had no fishes in my tank, so nearing what I thought was the end of the cycling, to test the water, I then introduced a stickleback into the tank.

It was alright for a couple days, but was soon dead. I later found out that though the general water quality 'seemed' okay, it was the toxins in the water that had caused the fishes death.

Could it be that's what had happened to your mates tank? Were there a discolouration in the sand, eg a growing 'black' area? Did the water smell 'badly'?

Sorry to hear of your friends losses.

 

[appleblossom]

hmm as i cant see the tank myself and wasnt there when i set it up ill have to ask him and see if he remembers.

Is there any way to test for other things in the water like this that could be harming the fish?? would a shop have the testing kit you would need to do it??

ps sorry for the long post above!

 

[Wyld-Fyre]

You could say I had learnt the hard way. From then onwards, I've never had sand as a substrate. IMHO, once bitten twice as shy.

During the cycling, I had performed one or two water changes, can't remember that far back, and that didn't help.

I don't know what testing kits there could be on the market. However, the simplest way of removing this problem is to stir the sand once every often to liven 'dead' (oxygen-deprived areas). Wish I had done this now.

Love reading long posts! (j/kg)

 

[FishDan]

I seriously doubt this case is toxicity due to gas pockets in the sand. For one thing, these pockets take a long time to develop. For another, they don' leach anything into the water. And for a third, they are toxic in large amounts and would need to be disturbed to kill your fish. The fish would also need to be in the path of the bubbles, unless the toxin wqas built up over an extended period of time and the toxin was all released at once. Personally, I find this highly unlikely here. Ask them if they noticed any smell, similar to sulfer or rotton eggs. This would not kill fish over a period of time, but all at once.

The coral may be a problem, as it will alter water chemistry. If it was found in the wild it may have brought nasties, though the boiling should have removed those. The coral iteslf could be deteriorating and releasing toxins into the water. I think the initial problem may have been caused by overstocking, and thus stressing of the fish. Swordtails get to about 4" long, so shouldn't be in such a small tank, though perhaps a pair of them and nothing else may have been okay. The German Ram should also have been in at least a 20 gallon tank. The platys, loach and shrimp would probably have been okay in a ten gallon tank.

Even if overstocking were not the issue, it is important to remember that in small tanks that water quality is much more difficult to maintain stability. The ammonia/nitrite levels could very well have been much higher during the middle of the deaths, and would have been reduced if testing was not done until after the last fish deaths. I also see the nitrate levels are pretty high, and that could have contributed to some of the deaths. Many shrimps are sucepitble to high nitrate levels. With such a small tank water changes should be performed frequently, and without "forgetting" or putting it off, as I said, water quality in small tanks can deteriorate rapidly and cause mass killings.

It is often difficult to figure out after the fact without watching the fish and seeing what went on why the fish died. Good luck!

\Dan