Why do my fish keep flicking?


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Bob Mehen advises a PFK reader whose fish have started flicking following a tank upgrade.

Q. I have recently upgraded my 60 l/13 gal tank to a brand new Rio 125 planted community aquarium (to which I add liquid fertiliser and CO2), with one Ram, one Bristlenose and around 15 tetras and rasboras.

Whenever the fish experience minor stress, like a gravel change (not a regular occurrence; just when adding a fertiliser substrate for my new plants), moving tank — or even the feeding of live food — they develop a gill irritation and begin to glance off the decor. Nothing looks abnormal and the gills aren’t reddened. There’s no fin clamping or gasping and no irritation on the rest of the body.

My LFS tested my water and declared it free of ammonia and nitrites. I change 25% weekly, using a dechlorinator. My GH is 16 and pH 6.4. Is it normal to have a high GH and low pH? I realise that this GH is not ideal for my Ramirezi, and could be stressing him, however I have had him for around two years now.

I’ve treated the fish at different times with a fungus, finrot and bacteria treatment and another for velvet and slime, but nothing has worked. I have recently read online that adding salt to an aquarium may help combat disease. Any advice?

Sam Walker, Gloucester

A. Flicking and gill irritation is a common problem but is not always related to a disease or parasite. You mention that you have recently upgraded your tank; how long ago was this? Did you 'cycle' the new tank before transferring the stock from your current tank? Did you move the filter or mature filter media from the existing tank across to the new, larger one?

I suspect that the flicking may well be down to a water quality issue rather than a parasite. If the tank is still relatively new and 'immature', (tanks take anything from six months to a year to be considered truly 'mature' in my experience) then there is a considerable risk of sudden fluctuations in water chemistry.

The move, combined with a potentially immature filtration system, a change of substrate and the addition of a range of medications, could all be irritating and damaging to fish; I would not recommend medicating a tank with anything unless you are pretty sure what you’re dealing with. The wrong medication can cause more harm than good to both fish and the beneficial bacteria vital for filtration.

Changing the substrate in a tank that is already home to fish can be very stressful, even if the fish are temporarily removed while it takes place. The substrate is home to large populations of beneficial bacteria that while not as vital as those within the filter can nevertheless help stabilise the tank's chemistry.

Add to this the fact that many planted tank substrates actually release a quantity of ammonia when first added and this could be at least a factor in the problems you are seeing. The liquid fertiliser and CO2 you mention adding could also cause the flicking if added in too high a dose or if you have insufficient plant growth to rapidly use them up.

You mention having the water tested at a local shop but I’d recommend getting your own test kit for ammonia, nitrite and nitrate etc., all of which could cause this problem. Newly set up tanks can suffer from spikes of these potentially toxic chemicals which come and go due to feeding patterns etc. It may just be that when you took the sample to the shop they were indeed clear, only for them to return later. With your own kit you can test daily to get a clearer picture of what is going on.

Adding salt is not a good idea and could cause yet more fluctuations of water chemistry.

You mention having an acidic pH but a high GH reading – this is not uncommon. Do you have a KH test kit, as this is more important? GH, (general hardness) is a measure of the dissolved compounds of magnesium and calcium and can only be changed by dilution with water with a lower GH reading such as reverse osmosis water. Your GH reading of 16 would be considered 'moderately hard' and while not ideal for the Ram it should not be a problem, particularly as you mention having kept it for two years previously.

KH, (also known as 'temporary hardness') is the reading that has direct effect on your pH as it is the measure of the buffering capacity of your water to resist change to its pH. KH is used up by the bacterial processes of the tank and over time will fall unless 'topped up' through water changes etc. and if not replaced the pH can crash to dangerously low levels. Knowing your water's KH will mean you will be able to tell whether or not your water is potentially open to sudden changes in its pH which again may cause the problem you are seeing.

The basic point I’m trying to make is that stability is the key in fishkeeping. Aside from regular water changes of the kind you mention, the less changes of all kinds you carry out; chemical, temperature, livestock, plants and décor the more likely it is that your fish will be healthy. I suspect given a prolonged period of settled tank life your fish may stop the flicking behaviour without further intervention.

Bob Mehen

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