Do you have a test kit? If so test for ammonia, nitrite, and nitrate and post the results. I'd bet that the nitrate level is high and that is what is feeding the algae and allowing it to take over. The solution to that is more frequent, larger water changes. Most of us change at least 25% of the water every week to keep the nitrate level low. On the schedule you've mentioned, not enough of the nitrate (which is the end result of the cycle as ammonia from fish waste is converted first to nitrite and then nitrate) is being removed and is available as fertiliser to feed algae growth.
As you're doing very small water changes, and only fortnightly, I suspect your nitrate level is high - do you have a liquid-based test kit to test this (and the other crucial water quality tests of ammonia and nitrite)? Weekly water changes of 25% (or anything up to 50%) ought to help considerably.
[ Edited to add: 2 pieces of almost identical advice arriving in stereo from myself and Fishlady. Hope this is helpful. :) ]
Thanks for your post and comments. I didn't realize that Clown Loaches needed a lot of space so I'll find another species if I re-stock.
I've four Danios and four Neon Tetras. Sorry but I'm not sure what species the Algae Eater is. The fish is about 10-12 cm long and a very distinctive orange colour. The fish is quite active and is happy to move around the tank at most times of the day. That's all the information that I can give you, unfortunately.
Water changes happen every two weeks and I take out about 5L of the total 60L (With ornaments etc. the water volume is probably about 55L) so it's about a 9 or 10% changeover.
The lights are on for about 8 hours a day. The tank is in the proximity of a window but it's north-facing so the tank does not catch much direct sunlight.
Solar operated fountain, sounds good, no running costs, what more can you ask for? If it were only that simple. If you have a quick search for "solar fountain" you will find lots of them....................all designed to go in a back garden tiny pond. I say tiny pond because at best the jet height is less than a foot (and that is if you are lucky) With a pool as big as yours you are going to need a jet(s) that are in the region of 5 foot tall, anything smaller and you will not be able to see it. The down side is there is not readily available a 12v pump (it is solar) that can do that, and if there were it would need an array of solar panels to generate enough electricity. There is also the consideration of where would you mount the solar panels? (Not to mention the cost of the solar panels)
You may want to read an article I wrote some time ago, its still as true now as it was then, Click Here
You would be far better off with a mains operated fountain, since it can have lights and run when ever you want it to.
If you do have any other questions, please reply here.
Really sorry to read about this. I too find it difficult to lose a fish, especially when so much effort is put in to help (the fasting, de-skinned peas, feeding regime, water changes, filter, tank, decor, addressing the dropping PH, and intentions for the future, were all good moves), and goldfish have so much personality that it's especially difficult. Its final demise sounds difficult to witness too - I've had similar traumatic goldfish deaths. It's also very natural to keep questioning (and berating) oneself over and over afterwards, about whether/how the outcome might have been different with different approaches, and, despite all the best intentions/knowledge at the time, it's very easy on learning more to have lots of regrets such as "if only I'd realised that earlier and done X/Y/Z", "how could I have not realised about X/Y/Z being such a big factor in fishkeeping", "it all makes sense in hindsight", etc. I do empathise a lot.
I agree completely with Fishlady's assessment of the situation - likely an internal bacterial infection plus exposure to ammonia and nitrite.
Another few factors might have contributed too - possibly the lack of filter/oxygenation of the water in the early days (although unlikely this as the fish lived on after this and there was improvement), the cycling process of the filter, the aquarium soil (I've read of a few cases lately where some brands leach ammonia although they're not meant to), the driftwood (may have contributed to the PH drop - but not necessarily and unlikely), possibly very low KH (if your water is very soft, and which may account for the PH drop), and the possibility that your 8-year-old child might have stressed an already-dying fish by inadvertently squeezing it or putting something in the tank such as unrinsed/soapy hands or food-stained hands or sprayed something in the room (you might know whether or not these are possibilities) which might account for the readings post-mortem (the nitrite spike itself couldn't be accounted for by the fish's death per se - it's more likely that the filter was going through its cycle and its stage in that cycle would account for the high nitrite). Sometimes aquarium salt can help mitigate against the effects of sub-optimum water quality which might have masked the severity of the situation.
Fish are absolute masters of just looking as though they're finally on the mend before the situation seems to go catastrophically awry - so I am sorry that your hopes were raised, only to be tarnished by what ultimately happened.
I know you'll be playing over the situation in your head, hence why I thought I'd deal with each possibility one by one. I do hope this is helpful and in no way makes you feel worse. *You absolutely did everything you could have with the knowledge you had at the time - please do remember this above all else!*
I suspect the fish had an internal bacterial infection (hence the stringy white poo), and then the presence of both ammonia and nitrite in the tank water over the time he was in there was enough to finish him off. Ammonia and nitrite both need to be 0 all of the time.
I’m grieving the sudden demise of a Shubunkin fish, which always had swim bladder problems and trying to understand what happened and where I could have gone wrong.
How it started: - Shubunkin fish kept in the pond; Had signs of swim bladder problems the day I bought it. Often swimming backwards, flipping, flashing etc…
- As the weather became colder, around November time, I noticed it lying on its side in the pond not floating.
- The 3 other fish (Shubunkins) were/are doing great in the pond.
Initial recovery phase: - I took it out of the pond with the water and quickly set up a 6 litre hospital tank (no filter system) and manually did daily full water changes once or twice a day with dechlorinated tap water and epsom salt.
- Kept it in a fasted state for a few days and gradually started feeding it de-skinned peas. It’s poo was white and stringy.
- Within a week, saw an improvement. It became upright again, however still unable to float and would move at the bottom of the tank. Would also sometimes flip and splash near the surface.
- Couple of weeks passed and I put in a small filter and did water changes after every few days.
- Nitrite was around 0.25 - 0.5 ppm and Nitrate was near 10-20ppm.
New tank and set up: - 2 weeks after I bought a new tank, long (60cm) and filled with 15-17 litres of water. Transferred the old water, filter and fish. Later added some gravel and a piece of driftwood in the tank.
- Water changes at this point were 50% and once or twice week.
- Food was one de-skinned pea and one stick a day.
- No signs of white, stringy poo. Would still flip and splash about near the surface.
- Fish was in this tank for approximately a month and half.
- Nitrite and Nitrate was similar to above, and this is the only time I did the ammonia test with a liquid kit, which came between 0.25 to 0.5 ppm.
- Ph was in the 7s.
Recovery in full swing (finally started to float): - Later I put in aquarium soil, decor and a dried leaf many days after that,
- A week after it finally floated and started swimming around in the tank. Note; it would still do the backwards swimming sometimes.
- After a water test, I noticed the PH lowered to the low 6’s originally from around 7. Screenshot attached. I decided to remove the driftwood and leaf and put in a low dosage of a PH buffer solution.
- I also observed the nitrite to be just above 0.5 ppm and nitrate to be just above 20ppm.
- Did a water 50% water change on the day of the results. Also put in some aquarium salt.
Day of the demise: - This was 5 days after the last water change. And I was actually going to one later this day.
- Sitting at the bottom of the tank in the morning, it did this often; Nothing seemed out of ordinary.
- Came home later in the evening, found my 8 year old with his hands in the tank and gently feeling the fish. This had happened for around 5 minutes. 5-10 minutes later the fish became vertical in the tank, gasping for air, then quickly swam to the corner of the tank where the filter was and violently gasping for air.
- Flipped on its side, and would not get upright. Then started shaking a lot of and did a white, stringy poo.
- Swam sideways to find shelter in the ceramic jar in the tank. I tipped it out of the jar, and it was still on it’s side; Didn't realise it was dead.
- Did a quick water test. The Nitrite level was 3 ppm, Nitrate was still above 20 ppm, PH was low a 6. The fish looked lifeless, took the fish out of the water; no reaction. And that was it. I'm assuming the spike was after the dead fish.
Couple of thoughts
I completely fail to understand what happened. It was so fast and sudden. I’m puzzled. Could it be the water? Did the water params look out of place in the photo (which I did 5 days ago before it died). I cross referenced the testing strips with other similar products and the various results appear to be in agreement.
Could my child have done something without me realising it? Or perhaps it was just bad timing?
Maybe there was an underlying issue which I never knew about. There always was a swim bladder issue.
I regret not doing ammonia checks, I was purely focused on nitrite and nitrate. I assumed that’s all I needed to follow, the API 5 in 1 strip kit made it feel like that. The PH eventually was in the low 6s, that makes me assume the ammonia would not have been toxic.
When the fish finally started floating and swimming, that seemed like the best indicator that I had done things right. And if I continued this way, I would have given it a full recovery and ready to go back in a larger tank or even back in the pond in the warmer months.
Your advice and expert opinions would be greatly appreciated. It's really heartbreaking and I'm finding it very difficult to let go, especially when there was such a positive sign.
You may be overstocked, definitely were with the clown loaches, who by the way were small for six years old and haven't lived long as the tank is way too small for them They grow to about 30cm long and should live 20+ years in the right size tank. How many danios and tetras have you and what species is the algae-eater? How often do yo change any water and how much each time? The other thing that makes green water worse is if the tank gets a lot of daylight from a nearby window and/or tank lights are on for too long.