Water test parameters

[NaSho]

Hi, I was just wanting to confirm the issues with my water parameters and hopefully confirm the advice the internet gave me.

We’ve had the tank a couple of months. We’ve recently added driftwood with some anubias, have ferns and mosses. I’ve also recently added red root floater and frog bit with a small pothos plant either submerged roots at the top. My aim is to ultimately bring nitrates down with the plants rather than water changes. The base is just stones/pebbles as the aquascaping started after we’d already setup the tank.

We have neon tetras, mollys, guppy’s and corydoras. We’ve lost one tetra, 4 mollys (2 bleeding heart and 2 balloon) and 1 guppy since we started, but we did have issues with ammonia and nitrites before we were more educated. Most recently and at the time of water measurement we lost a guppy. This was after a water change and I rinsed the filter sponge in tap water, which I believe may have caused a spike in nitrates. I also know that there are health issues with balloon mollies due to their shape, we won’t be buying more.

Water temp 24
pH 6.6-6.8,
ammonia negative,
nitrite negative,
nitrate 20ppm,
KH 71.6ppm,
GH 214.8

We use the API master test kit, plus the API GH and KH separate kit.

According to the internet our pH is too low for some of the fish and also our KH and GH are low. It said to add crushed coral to the tank. I would just like to confirm that this is the correct action to take. I don’t want to add bicarbonate as I know it can be fiddly and harm the fish if you get it wrong.

Many thanks

 

[Andy Sager]

Let me start by saying that you change water for more reasons than just reducing nitrates. Water changes should be part of your regular routine whether you have nitrates or not. There's no issues with letting plants utilize the nitrates that are produced by your fish so that means that you want to be careful not to do too much of a water change that you eliminate totally the nitrates to the point that the plants suffer.
As for the pH and your fish, the Guppies and Mollies do better in harder more alkaline water. The Cories, depending on which type you have, can have a range from mildly acidic ( 6.5 +) to a more alkaline pH ( 7.8) and like some flow/current in their water. The Neons are the outlier of the group because they prefer a more acidic water. What you most likely have are tank bred Neons and they seem to be more adaptable to a wider range of parameters but there are no guarantees there. So the problem is you have a collection of fish that like different water parameters so if you fix the water for one, you may be damaging the other fish. So in your case, I would not add crushed coral because your wood will be trying to acidify and soften your water so you will have 2 forces countering each other in a never ending battle that neither one can win until the other loses. What's best is to choose fish that like the water parameters you naturally have so that you are not constantly adjusting.
Regarding the Mollies and Guppies, Balloon Mollies are purposely bred to be that deformed so yes, the fish in the long run do often suffer from internal damage (i.e. organ issues, low birth rate, etc) So your deaths may have had nothing to do with your water change or filter " oops". ( BTW, Killing off the nitrifying microbes from the tap water would lead to a spike in ammonia, not nitrates. The higher nitrate level would come after the ammonia had been converted to nitrite then nitrate and the damage is already done if you have an ammonia spike. ) Guppies unfortunately, have been bred to the point that they are more fragile so again, it could have been the fish themselves vs something in the water or what you did. As previously explained tho, Guppies and Mollies can interbreed so if there are too many males than females, they can pick each other off so your deaths may REALLY have had nothing to do with anything in your tank or what you are doing. It's just guesswork at this point. You either want all males or many more females than males.
Bottom line, if you want a more alkaline water, you should remove the wood. If you like the look of wood in the tank, get artificial wood instead. If you want a more acidic water with fish that like and can handle a more acidic water, leave the natural wood in the tank and exchange the Guppies, Mollies and potentially the catfish. Keep in mind tho that acidic water slows or stops nitrification so you won't have much nitrates for your plants to utilize and you will be doing more water changes to keep the tank clean. The positive to a more acidic tank is that fish do not suffer if there is a rise in ammonia because at a pH under 7.0, toxic ammonia is converted to non/less toxic ammonium and it takes a whole lot of ammonium to be toxic to fish.

 

[NaSho]

Thank you very much for that, seems we have some decisions to make in regards to how we choose to proceed. Much appreciated.