Thanks. Problems of similar severity to the PH crash are occasionally to be expected when adverse weather conditions occur and you're trying to keep medaka or other fish outdoors. I've had tree branches blown down in strong winds; toxic leaves falling in the tubs; blocked outlets in the tubs causing fish to be washed out of the tub during heavy rain. I've had a bird dying in the pond and polluting the water; etc; etc. I've seen where people have had their tubs destroyed by racoons and similar animals. As a general issue, water temperatures in my tubs may reach about 35degC next month at least half the time. The resulting low dissolved oxygen content at those sorts of temperatures will start to put stress on the fish. At temperatures higher than that, the dissolved oxygen content decreases further e.g at 40degC, there may be considerable stress on the fish. If I have, say, 15 medaka in a tub then I'd expect to lose at least 3 or 4 or even 5 of the weaker fish by the end of the summer due to high temperatures and/or high rainfall and/or high winds. I've probably got more than enough eggs already. No more goldfish ..... the bioload produced by those 5 goldfish was probably equivalent to the bioload produced by 100 medaka ..... at present, I'd rather have another 100 medaka in the pond rather than add new goldfish.

Respectfully, I have a different understanding of the pH of rainwater. My knowledge is limited, but it appears that in pristine areas of the world, theoretically, rainwater has a pH of 5.6 due to precipitation dissolving CO2 to form weak carbonic acid. In areas such as Tibet there is alkaline dust in the air and rain pH may be above 7.0. In tropical rain forest areas there are organic aids in the air and rain pH may be about 4.5. I don't know anything about the UK but this 2022 map nadp.slh.wisc.edu/filelib/maps/NTN/pdfs/2022/pH_2022.pdf shows rain across the USA is within a pH range of 5.0 up to about 6.5. In my area rain pH is about 5.0.

Thanks for the suggestion. That's an option, but I've been happy enough with my overall medaka keeping results so I haven't previously introduced that added complication. However I'm now trying something similar and possibly that'll be the subject of my next video

@@km-qh3rs sounds good. im new to medaka raising my first lot indoors. wish I had a garden to have pots like yours.