How closely should I try to match my water chemistry to what I am reading is the ph and how hard or soft the water is for different species? I would ideally not like to mess with my water, but it doesn’t seem like too many killies match what I have. Will they not thrive, not breed, or not survive depending on the differences? Does anyone have any suggestions on species I should try without needing to alter my water?
Any input at all?
Your water is moderate and suitable for most killifish species in the hobby. You can keep and breed 80%-90% of the species in common circulation with no changes. The more difficult Aphyosemion and Funduolopanchax species might benefit from softer more acidic water if you are having trouble breeding them. Species that have been in the hobby for many years are generally better adapted to a range of water parameters, versus wild-caught or F1 which may require more specific conditions.
The local tap water where I am in Southern California is fairly hard and alkaline, and is objectively worse than yours for most killifish (but it’s excellent for Nothobranchius). I raise most of mine in tap water whenever possible, and they breed well and do fine. I agree with your inclination to not mess with the water. Most species can adapt and tinkering with the water chemistry is high maintenance and risky for the fish. Large fluctuations can cause more problems than allowing the fish to adapt to stable (but not ideal) water conditions.
If you do need to soften or acidify your water to get a fish to breed, do this gradually. This can be easily accomplished with tannins and does not require RO water, although RO can make it easier to get the pH down. I personally use catappa leaves or peat moss in a bag, but oak leaves would work and is locally available for many AKA members https://aka.org/general-tank-additives-oak-leaves-another-aid-to-conditioning-water/
If you do modify your water, you need to test it regularly because water chemistry will change over time. RO water is especially prone to swings because it lacks any buffers. Big fluctuations during water changes is a risk, and unless you are changing smaller volumes >20%. One trick is to keep your fish in bigger tanks (10 gallons vs 3 gallons) which stabilizes the water parameters and requires less frequent maintenance. You would also need to test and condition the water you use for water changes to match the tank conditions. I have lost fish to shock after changing out ‘bad’ water with ‘clean’ water because the change was too big of a shock.
A final note on temperature. Some species such as Diapterons are temperature sensitive and prefer cooler water in the 60s. I can keep them alive in my tap water, but they won’t breed for me. I gave up on keeping those because my tanks get to 78F in the summer months and they fade in the heat.
