I have been keeping fish since 2014 and have never had any major mind-boggling problems until very recently. I am currently keeping three fully grown freshwater angelfish that are approximately four years old, six harlequin rasboras that are almost six years old, four cardinal tetras and three rummy-nose tetras, both only a year or so old. These fish are all fine, eating normally, active and curious of anything inside or outside their tank. I currently have three pieces of driftwood, three aquarium-safe plastic ornaments and one river rock decorating my aquarium. The substrate currently is Fluval Stratum Plant/Shrimp substrate (I plan to plant my aquarium when I have sufficient funds to do so). My tank measurements are L90, W37, H45 cm. I perform water changes every 1-2 weeks depending on the pH and Nitrate levels. My pH usually sits around 7 or 6.8 and I do a water change if it drops lower than that. I have no ammonia or nitrite in my tank, no copper either. My Nitrate levels are currently just below 20ppm.
My water changes had been almost solely completed with tank water when I first began keeping these fish. When I first kept fish in a smaller tank, I had guppies and a female Bristlenose Catfish. She passed a few months before I moved my fish tank from the Gympie Region to the Sunshine Coast. The only change I made to my fish tank after the move was to swap the river-pebble substrate out for a fine black quartz sand. Since moving to the Coast I have been unable to keep a Bristlenose alive in my tank for more than a few days. All of my other fish mentioned above are fine and healthy, I even had live plants in the tank for two or three months. Because I didn’t want to kill any more catfish, I tried keeping an Apple Snail in my aquarium, which died after two days I have taken a sample of the aquarium water and substrate to the local aquarium shop and they could find nothing amiss with either the substrate or my water and were quite puzzled — as am I — with why my catfish keep mysteriously dying. With the quartz substrate I did notice that two catfish I had tried to bring into the tank (on separate occasions) developed a twitch in their tail shortly before passing away. There are no traces of salt or copper in the water (which was a suspicion of mine originally).
Two weeks ago I moved to another town within the Sunshine Coast Region (still using town water) and changed the substrate to Fluval Stratum Plant/Shrimp substrate as I want to create an aquascape in my aquarium. My father has his own 8ft fish tank in which he keeps African cichlids, clown loaches and Bristlenose catfish that breed like crazy. I caught an infant catfish from his tank (around two centimetres or so long) to trial in my own tank with the new substrate. I added the catfish four days ago and it had passed sometime this morning. It had none of the symptoms I had previously noticed with other Bristlenoses (no twitching), but I did notice it was breathing quite erratically last night. Otherwise, it was very active — if a bit shy — in the days leading up to it’s passing. Before I added the catfish to my aquarium I performed a water change, then put about 300ml of my aquarium water into the container holding the catfish with my dad’s aquarium water every 15 minutes. I repeated this five times before catching the catfish in a net and putting it in my aquarium.
The longest I have managed to keep a Bristlenose alive since moving is three or so months, which was after I added activated carbon to my filter as suggested by the aquarium shop owners after taking a water sample there. I am now due to replace the activated carbon. There is an orange/brown algae growing on the surfaces of my aquarium (substrate, driftwood, rocks, ornaments and glass) that grows very quickly despite my constant scrubbing of these surfaces to remove it.
I really am puzzled as to what is causing my bristlenoses — and snails — to die after only a few days of purchasing and acclimatising them to my tank. Any advice or help would be extremely helpful as I really love keeping bristlenoses and snails!