I have two 15 year old goldfish in a 180l tank. In August last year one of the goldfish developed some strange lumps which eventually fell off (I think it was Lymphocystis) but it now has a growth over its eye. The growth started to bleed and so I added some Melafix to the water which seemed to heal it, although the growth is still there. The other goldfish seems to be prone to fungus growth atm which has not been responding to treatment.
Up until a couple of days ago both fish were swimming around quite happily but they are no longer moving very much. The fish with the growth spends most of its time sitting on the bottom of the tank, although it does come up to eat. I know this is a probable sign of stress, but I am struggling to work out what to do. I noticed this evening that the water temperature was 25 degrees, due to the warm Summer weather (I don't use a heater). Normally the temperature is around 18-20 degrees and so could this be part of the problem?
My tank stats are below.
* Ammonia level - 0 * Nitrite level - 0 * Nitrate level - tbc when new test kit arrives, but in the past my tap water reading has been high (London tap water). I have always struggled to reduce the nitrates but the goldfish have never been affected. * Running an internal and external filter. I clean the external filter monthly (using the tank water) and the internal during the weekly partial water change. I changed to a weekly tank clean, because the tank was getting too dirty (the goldfish are very large!). * Artificial plants, because the goldfish ate live plants and made the tank messy. * Light is kept on for 5 hours a day * I've recently switched to feeding once every 2 days, because too much food was in the gravel. As far as I can tell, all food is now being eaten and the gravel is much cleaner.
I don't think it's the temperature as goldfish are tolerant of quite high temperatures for short periods. The biggest risk with warmer water is that it holds less dissolved oxygen, but if that was the issue the fish would be gasping at the surface rather than sitting at the bottom.
High nitrate is a common cause of bottom-sitting, so get the nitrate test as soon as you can and see what it reads. Ideally for goldfish it should be less than 40 ppm.
Thank you for your reply Fishlady. The test kit arrived today and the nitrate level was between 40 and 80 (the two red colours looked very similar!). Interestingly the tap water reading is around 20 and so the source nitrates are lower than last year. My tank is due to be cleaned this weekend and so the nitrates will hopefully be reduced, but it looks like my tank may need a bit of a helping hand to keep the nitrates low.
Do you have any experience of NitraZorb? I like the fact that it can be recharged using saltwater rather than bleach, although I am not sure where in my filter it should be placed (I have a Juwel 180l tank). Or can you recommend any other products?
After doing some more reading I'm also worried that reducing the feeding to once every 2 days may be cruel. The gravel is cleaner and the fish certainly don't seem to mind eating less frequently. Should I return to once a day?
How often are you changing water and how much each time? The recommended minimum is 25% a week and up to 50% for fish like goldfish. With regular large water changes you shouldn't need any nitrate reducing media. If you do decide to use it, Juwel sell nitrate reducing sponges for their filters, but they need regular replacement.
Sorry for the delay in replying. I do a 50% water change once a week. Any less and the tank won't stay clean, because my goldfish are very large and produce a lot of waste. My lfs, who normally offer useful advice, told me that I shouldn't change more than 10% each week, but I've found other blogs online that say that large water changes are fine. It's very confusing to have such conflicting advice!
My goldfish perked up significantly following the tank clean and have been in good spirits today. The nitrate readings haven't really gone down and so I'm not sure why the fish are happier but I'm not going to complain. Perhaps the water temperature was lowered a little by the water change?