We have had a Pleco in with one commet and four fancys for two years now and all have lived in harmony, we have a large 60 gl tank a juwel vision 260 and a it needs a lot of decor we spent loads on real plants and the daft things just used them as another food source and scoffed the lot so not liking the look of a bare tank we bought a huge artificial plant off ebay and after a few weeks it's caused the water params to whack out I feel there was something in the base not right to mix with water but thats just my gut feeling.
We noticed the fish flashing and the commet Mokey began to get some damage to his scales due to rubbing himself on the substrate, at that point we noticed the pleco making a bee line for him and trying to suck onto him..Mokey is now not looking so well his fins are laid back to his body.
We have put a couple of drops of melafix in the juwel tank and whipped the Pleco out and he is now in a spare 4 foot tank on his own..my question is..is this going to be the start of the plec going bad or did he just use the oppertunity to pick on a ill fish and can anyone else think of anything else we can do to bring the tank back to optimum conditions, nitrate reading is still 50 after two big water changes friday he did a 50% yesterday he did 60%..and my patrner is about to do a 30% today we dont want the tank recycling as we are going on our hols next sat and the person watching the fish does not want to be doing water changes..should we keep the pleco on his own or even take him back to the shop he is around 8inch's and the commet around 10inch's both are around 2 years old...hope someone can advice...Phe

First of all, if you do 3 x 50% water changes or 2 x 75% water changes that should bring your nitrAtes down to 13% of the original reading.

Secondly, the only plecos recommended for goldfish are bristlenose and rubbernose plecos. These don't grow as big and for some reason usually leave goldfish alone. If yours is a common pleco I would keep him separate from the gf from now on. Once they start to attack it's a behaviour they are likely to repeat.

It is odd that a fake plant would cause the fish to act sick unless it's not designed for aquarium use and then it could be made of something toxic. Either way I would remove it and replace it with some fake plants from the lfs or get back into live plants.

I would recommend keeping up with the water changes and the melafix but if the fish continue to flash and rub they may have some form of parasite, although where it could have come from I have no idea. Water changes and gravel vacuums should not crash your cycle as most of the bacteria live in the filter media.

Even without the plec you are overstocked in the tank. I am assuming as well that you are just relying on the juwel filter on its own?
If so then you need to add another powerful filter so you arent doing so many water changes.
Do you do gravel vacs as well?

Thanks for the replys 1st of all I didnt think we were overstocked as we allowed 10gl per fish I thought that was the rules?..has it changed?..we have the juwel filter and a fluval 4 running as we felt the filter that came with the tank was not so good..and yes we vac once a week.

The plec is a sailfin but yes we have him in a 40gl on his own bless him we have had them all together for two years without probs..we bought the plant off ebay and the guy who sold it us said it was for ok for tanks but I realy dont think it was so I have thrown it away it cost about 15 quid so it wasnt a cheap thing..yep we will keep up the water changes and the melafix as this seems to be the only cure.
Yes they are still flashing so tonight we are going to do another change and vac.
The tank has been running since december so it is well established we just wondered if anyone had any other ideas how we could get everything running as it should be..many thanks for your help...Phe

PS Erika my good friend I missed you too and thank you for the birthday greetings hope your snails are ok we still have several thousands of them and loving them all..LOL..Phe
PPS I only have a couple more post then I can join you LOL

A 10 inch comet will need around 40 - 50 gallons for himself, you might think that extreme but thats a big fish.
Im pleased you have another filter on there as the juwels just arent suitable for goldfish when run on there own.
High nitrates can cause fish to rub, have you added anything new apart from the plant?
Keep going with the large water changes and test the water before you do a water change and if you test the nitrates from the tap then this will help you know what to aim for.
Do you have aquarium salt?
I take it the plant you bought was brand new and in its own packaging and not from another tank?

I agree that the plec has to move permanently because as they get older they eat less algae and green foods and go for fish instead. Feed your plec some shrimp now and again and make sure he has plenty of bogwood to rasp on.

Hmmm yes he is a big fish and the others we bought at the same time are only a quarter of his size people do a double take when they see him and ask me if he is a goldfish or a pond fish LOL..Rayman the pleco looks a bit lost on his own but if its best for the other fish then he can have the tank to himself..funny thing is he never went for the other fish just Mokey the biggest one..the plant had been used and I did give it a good wash before putting it in our tank but I guess a lesson learnt the hard way..Pleco has shrimp pellets and spirulina pellets and algea wafers.
Nothing else new Sandy just the plant, when we removed it,it stunk bad I cant describe the smell but it wasnt just tanky it was awfull..I feel really bad as we wanted to make their tank a nice place for them to live in..we have just done all the water tests and all are in the normal range but the fish still look like they are suffering so we are doing a water change again.
We dont have any aquarium salt but we can get some if it would help..how much do we use and how often..thank you for taking the time to help us we have had these fish 2 years and we love them to bits and dont want to loose them..Phe

Its hard to say what it brought in but if you keep doing the water changes of 50% each day for a few days hopefully the lower nitrates will help.
If its a parasite then you may need to salt to .3% for a couple of weeks. Thats 1 level teaspoon per gallon predissolved every 12 hours three times, and you will have to remember how much water you take out so you can replace the salt.
If its bacterial then the best thing is the water changes to keep the water in good condition.

Yep will do thanks for your help..Phe