Fishless Cycling Problem

Whitespot looks like the fish has been sprinkled with salt.

Whitespot is caused by a single celled parasite. It has three stages in its lifecycle.

The first stage is attached to a fish. When it first attaches we can't see it but it soon grows a sort of shell around itself and we can then see it as a white spot. Inside this shell the parasite feeds off the fish's tissue and grows and grows. This is stage 1, and because of the shell, medication can't get to it.

When the parasite has eaten enough, it drops off the fish, still inside the shell, and divides in two again and again until there are hundreds of them. This is stage 2, and again the shell protects it against medication.

Then the shell splits open and hundreds of tiny parasites go swimming off to find a fish to infect. This is stage 3 and is the only stage where medication get at it.

There will be parasites in all three stages in the tank at the same time which is why you have to follow the medication instructions to the letter. There must be some med still in the water when the very last shell splits so the 'baby' parasites can be killed.
Some medications tell you to increase the temperature of the water. This is because the parasites go through their life cycle faster in warmer water.


There is a body of thought that all tanks have whitespot parasites in them but the fish have developed immunity to them. But if the fish get stressed it lowers their immune sytems and allows the parasite to infect the fish.

Besides the actual spots, other signs include a fish continually flashing - that is flicking its body against objects in the tank. This is often the first indication of an infection as the parasites are too small to see at first, and they usually start off on the gills where we can see.



Whitespot is a very common infection. Most fishkeepers have it at some stage. Well, the fish keeper doesn't his fish do.

Asked at LFS about single white spot on nose and they didn't know what it is either. One thing I do know is he is a hungry fish. Others still off their food but showing signs of getting better so hopefully no more fatalities. While I am using medicine, should I avoid a small water change unless necessary?

Got some fish for the quarantine tank today, but nearly had a fatality, one made a jump for freedom and landed in dirty water bucket with no water in it. Fortunately added water quickly and finally got him in tank after he tried to escape again.

Also, fish often develop markings from scuffles eg competing for food or sparring, so that's another possible explanation.

Have I read this correctly - you've bought more fish? Or do you mean you've moved some of the current, worse-for-wear ones into the QT? Hopefully the latter as you definitely need a period of time (eg a couple of months, as previously advised) with no fatalities/casualties to get to the root of the problem in the main tank and ensure it settles down. Otherwise, you may find you'll need another QT- one to quarantine new fish and one for hospitalising any ill fish...

Let's hope we can collectively help you get to the root of your problems and resolve them, so keep us posted. 

Sorry guys, urgent help needed. Think one of the fish in the QT tank is showing signs of stress, as he is swimming upside and flying round the tank. Any ideas what I can do? Water was fine this morning but will of course check now. But anything else you can suggest?

Rasboras, just checking ammonia and nitrate now. Think one is dead and another nearly there. Other two are ok. Will post test results in 5 minutes

Wow, lost all 4 in quarantine in 30 minutes. Makes me want to give up!!! Water is perfect, only thing was the paraguard I added yesterday but it fades away after 24 hours.

Not sure which way to turn now. 3 Rasboras in main tank all looking happy.

Just don't know what to do next. Feel like just doing what my dad did 30 years ok, add in a load of fish and they all survived.

It could still have been the paraguard. It would have got into their bodies before it faded away.

What you report sounds like what happened to my beckford's pencilfish a few years ago, just not quite as fast. I added melafix and pimafix to the tank to treat a sickly honey gourami and came back 45 mins later (I went to watch Countdown) to find 5 of the 6 pencilfish dead and the 6th almost dead.

If you decide to continue with the QT, don't use any medication unless the fish show obvious disease symptoms. Just make sure the water is clean and ammonia/nitrite free. Every chemical we add to a tank, even dechlorinator, gets into the fish's bloodstream and tissue. The less we add to the water the better for the fish.




What chemicals do you use routinely, and what else have you recently added to both the main tank and the QT? You said you have used paraguard, but list everything else including the brand of dechlorinator.

And also, does the water supply go through a softener of any type; does the water you use come straight from the mains or from a storage tank etc. I know some houses were built so that only the kitchen cold tap came from the mains, all others came from the tank in the attic. Do you use hot tap water to warm the water going into the tank? And if so, what kind of hot water system do you have - combi boiler or cyclinder in the airing cupboard?


Just trying to find a clue somewhere........

Ok, in the QT tank only chemical was the Seachem Prime. Then added the paraguard yesterday, but supposedly a very weak dose.

In the main tank, again Seachem Prime at water changes and currently using the white spot/fungus medicine to try and resolve illness in main tank. Got one more dose to give on Thursday, then will do a small water change at weekend.

Water comes straight from mains, hot water from tap is from a combi boiler.

Lots of people use Seachem Prime with no ill effects - and it says somewhere in the instructions how much it can be overdosed.

The whitespot med should be used as instructed and the course finished. If the people who say the parasite is in all tanks all the time are right, you don't want to run the very small risk of creating a medication-resistant strain by stopping the med too soon.

Paraguard is a med I have not used and don't know much about, so I've googled it. It contains "aldehydes, malachite green and fish protective polymers". The list of fish that may have adverse reactions does not include harlequins (just the usual scaleless fish such as loaches and rays).
Unless you have overdosed the paraguard (for 20 litres you need 2.5 ml or half a capful) the only thing left is that the harlequins do react to it but that Seachem deny it in the way that API deny that pencilfish are sensitive to melafix or pimafix or perhaps the combination of the two.





Does anyone in the house use aerosols of any sort in the same room as the tanks? Do you use air fresheners? Have you been painting recently? Do you have other pets that have been treated for fleas? Do you use handcream or something like that before putting yuor hands in the tank? I'm grasping at straws to work out what is going on 

Before putting your hands in the tank I would wash them thoroughly with plain water. Use the anti bac soap afterwards by all means, that's what I do, but remove as much as possible before going into the tank.

It has been known for flea treatments to get in the air and from there into a tank. This could be a contributing factor.

The boiler would only be likely to affect invertebrates and particularly if there was a lot of new copper pipework put in at the same time. Copper kills shrimps and snails.
It is the older hot water cylinder type that can harm fish because they have a header tank in the attic which, despite them being supposed to have a screen over the top to prevent creatures of all sizes getting in (thanks Andy the Minion for that piece of info) not all of them do, including ours. All sorts of creatures can end up dead in unscreened header tanks 



It could well be the small numbers causing the harlequin's behaviour. Being in a group that's too small causes stress in shoaling fish, and this can affect their behaviour.

At this stage, I would risk putting new fish straight into the main tank. Once you have lot of fiish, then it is worth quarantining new fish, especially if the fish you have were quite expensive.