Thank you so much @xXInkedPhoenixX and @Patrick_Gfor the super fast replies. You were both absolutely right . Luckily I've just purchased the test kit so I'm hoping it didn't affect the accuracy of future uses.
this poor tank was and still is in pretty bad shape. The water and side of the tanks were completely covered in algae and the anubia is covered in black beard algae. I guess the previous owner just ran out of time and wasn't keeping up with water changes. I've already performed 2 25 percent water changes since the move on Tuesday but I'm worried about stressing them out even more. I think the tank might be overpopulated as it has 3 adult mbuna cichlids 2 cuckoo catfish about 10cm long and a 10cm bristlenose Pleco and a 15cm bristlenose pleco. Can I ask your thoughts on whether that's too much?
thanks again in advance