Fish Rubbing Gills On Gravel - Help Please!

[GreenA]

Hi everyone.


Both my male guppies have started to swim to the bottom of the tank rubbing their gills on the gravel and pushing themselves up again. They don't do it frequently just every now and then but it just looks wrong....

Tank details:

90l tank,
6 fish (2guppies (m), 2mollies (m/f), 2swordtails (m/f))
water changes at the moment between 50-90% depending on ammonia level


(checked with API master test kit)
ammonia: >0.25ppm (checked twice daily so it does not have a chance to spike)
nitrite:0ppm
nitrate:5.0ppm
pH:8.2 (constant)

filter is on and made for 100-140l tank
water temperature a constant 25°C however, today it went up to 28°C as it was very warm today.

the fish look healthy, no white spots, no swollen gills, good appetite and they are quite active swimming about, picking on plants....it all seems normal apart from the occasional rubbing..

I have live plants in the tank and other than water conditioner for water changes no other chemicals.

Does anyone know what it could be? Do I need to worry?

Thanks in advance.

 

[Hermithall]

Your tank is showing 0.25ppm ammonia which is a low reading but indicates your filter's bacteria colony is struggling to consume the ammonia. The low levels of ammonia could explain your guppy's behaviour and you'll need to get that ammonia down to zero. Just keep up the water changes while monitoring the ammonia levels as you're doing (always dechlorinate new water). Check your tap water too out of interest - some tap water contains ammonia.
Is the tank cycling or an established set-up. You're not overstocked, so if the tank is established you might have a problem with water flow through your filter media - check it's not gunged up. Feed sparingly as a general rule, and very sparingly while you have this ammonia problem.