Will do the water tests, the water is tap safed, we do a 20% water change every two months, water temp is 26.5 degrees. no salt in the water. The tank is approx 18" deep and about 22" high (odd size tank, I know)
Haven't seen any agreessive behaviour between the fish, the blood parrots tend to keep out of the way of the BGK, although i have noticed the plec has been bothering him a bit recently and keeps attaching himself to him (like when they suck on the glass). Stabby quite clearly doesnt like this and usually buggers off to the other end of the tank.
The tank is due for a clean, but will cleaning it now while he's already under stress be the right thing to do?
You will need a wider tank in the future, preferably at least 24inches wide, since the knife fish can grow to 20inches+ long so will have difficulty turning around in a tank less than 2ft wide.
The pleco problem is a problem that won't be helping the knifefish in any way and you don't want the knife fish to be getting stressed out, do the pleco and knifefish both have their own caves where their can take refuge in or do they have to share the same cave or have no caves in the tank at all? What do you feed the pleco and how much on average and how large is the pleco?
A once 2monthly water change though is not anywhere near enough i'm afraid- you should really be aiming to do a 30-60% water change once a week with fish like yours. Not during regular enough water changes means that organic waste will build up in the tank (particularly in the substrate) over time which can harbor diseases and effect the ph of the tank, so it is important to do regular water changes to help ensure these problems do not come about- during regular water changes is more about making sure the tank and its inhabitants stay in optimum health in the long term
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You will also see better growth rates from your fish by doing more regular water changes too- many fish in the hobby come from habitats in the wild which experience dry and wet seasons, and many fish will not grow much during the dry seasons for numerous reasons- not doing water changes for months at a time will create dry season conditions in the tank (like build up of organic particles and matter, which the fish can sense) and so the fishes growth will slow down and may even become stunted in the long term.
The best thing to do right now until you can test your water quality is to clean the substrate in the tank, do a 30-40% water change with dechlorinator, and clean out the filters sponges in old tank water taken from the tank (remember not to over-clean the filter sponges though, just clean them enough to make sure the filter runs smoothely, if you over-clean the sponges or clean them in undechlorinated tank water you could kill off too much of the beneficial bacteria residing in the sponges, which could cause the tank to mini-cycle etc).
The water change may cause a minor amount of stress to the knifefish while you are doing it, but it will have a lot of benefets for the knifefish so is well worth doing
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