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Discussion Starter · #1 ·
Hi everyone

I hope someone might be able to help me out here. So far I've only had a planted tank for caridina bee shrimp using Amazonia aqua soil and remineralized RO water. These shrimp need a very low KH of 0-2, so I've kept them at 0 KH. This works well with the soil since its buffering effect would slowly strip KH from the water anyway. Paradoxically, these sensitive shrimp also need very stable parameters, but the pH will supposedly swing more dramatically the lower the KH is. I am not injecting CO2 so I am only seeing smaller changes from day to night.

The thing is that I want to set-up a planted tank with fish using Amazonia (ver. 2) aqua soil, soft water and pressurized CO2. The soil seems very popular for planted (fish) tanks. But many online sources will state that a tropical fish tank needs a KH of 4-8 and that a lower KH can be dangerous, even lethal to fish.

I don't understand how this works. Do people keep fighting the buffering capacity of the soil by adding more KH to the water as it is gradually removed by the soil (like with crushed coral)? It seems counter-intuitive to pick an active substrate only to exhaust its buffering capacity. Do they just use it as an eventually inert, but nutrient rich plant soil? Or do people just let the KH drop to a low level, even 0, without fighting the buffer?

I've read somewhere that changes in KH are actually more dangerous to the fish than swings in pH and that it would be better to let it rest at 0. Is there any truth to that? Has anyone had experience with keeping fish at 0-2 KH? I was considering keeping fish like otocinclus or chili rasboras with my caridina shrimp, but I am not sure how people do that if they're incompatible in terms of KH levels. 4 KH would apparently be too high for the shrimp, but lower would be too low for the fish.

Thank you for any advice and insight!
 

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Discussion Starter · #3 ·
That's reassuring to hear! It would mean I could keep the same water parameters as in my shrimp tank - that is pH around 6.6, GH 5, and KH 0. Only the temperature would be slightly higher.at around 25 C/77 F. I am planning on keeping schools of cardinal tetras, corydoras, otocinclus, and perhaps a single male honey gourami or cockatoo dwarf cichlid as a "centerpiece fish". It's a 175 liter/46 gallon tank. They should all do well together in somewhat acidic, soft water as far as I can tell. I am not quite sure if the cockatoo will accept the corydoras even with caves and plants, but supposedly they are more chill when not paired up and breeding.

My concern came from articles like this:

It stresses the dangers of having a low KH a lot.
 

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Discussion Starter · #5 ·
all those fish are very good for softwater tanks. though a group of honey gourami maybe 5-7 would look quite good. a 46 gallon is very big i wouldn't be too worried on overstocking
I am aiming for a large school of cardinal tetras though (like 25), around 10 corydoras, and around 10 otocinclus since they all do best in schools. With a honey gourami that puts me at 102% stocking level according to AqAdvisor. But then again, my filter capacity is at 371% and they're all small fish living in different sections of the tank.
 

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I would aim smaller numbers for the honey gourami, if you go with them. I have battery acid for water (0-2, 80 dissolved and ph around 6.5 out of the tap). I use my tap water for my tanks and don't have any problems. My 40B has cardinals, rummynoses, a rebellious oto, cories and a couple left over endler/ guppy hybrids (I do not suggest keeping livebearers like this, but those were feeders anyway and my hubby and daughter were impatient with me not populating the tank). Stick with soft water fishes and slowly drip acclimate. Make sure the place you're getting them from doesn't have hard water, that's another big one that will help you reduce losses.
 

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Discussion Starter · #8 ·
I would aim smaller numbers for the honey gourami, if you go with them. I have battery acid for water (0-2, 80 dissolved and ph around 6.5 out of the tap). I use my tap water for my tanks and don't have any problems. My 40B has cardinals, rummynoses, a rebellious oto, cories and a couple left over endler/ guppy hybrids (I do not suggest keeping livebearers like this, but those were feeders anyway and my hubby and daughter were impatient with me not populating the tank). Stick with soft water fishes and slowly drip acclimate. Make sure the place you're getting them from doesn't have hard water, that's another big one that will help you reduce losses.
Thank you for your advice as well! Very useful to a total noob like me trying to avoid too many beginner mistakes.

With honey gouramis I read that they too (understandably) can be aggressive when breeding and guarding their bubble nests. That's why I was thinking a single male since they are supposed to be peaceful fish otherwise. I really just want easy-going fish to create a nice community tank without any of them being stressed out or even injured or killed. Turns out that may be harder than I imagined if you want a slightly larger "centerpiece fish" to go with your cardinal tetras, corys and otos. Like I said, this will be my first fish tank and I have zero actual experience with keeping fish. Just one shrimp tank.

As for acclimating fish I just began opening that can of worms, and it seems to be a controversial topic as well. I'll derail my own thread a bit here. Popular YouTuber Rachel O'Leary advocates the "drop and plop" acclimation method and seems to make compelling arguments for it. She seems very knowledgeable and experienced. But I think most LFS in my country (Denmark) keep their fish in tap water which is rock hard and high pH. I measured my tap water at 850 μS or 544 TDS recently. In the past I've measured it at 16 GH, 12 KH and 7.8 pH (not degassed). Plopping any fish from that water into a soft water tank like I plan would surely be very stressful (if not lethal) to them? Also, unlike a professional fish keeper my fish wouldn't have to endure long transportation times from the supplier and the associated ammonia contamination of the bag water should be much less. But I might have to try to find a LFS or even a private breeder that keeps their fish in soft water more comparable to my tank.
 

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I strongly recommend against the drop and plop. If you're going from rock hard to very soft you will kill your fish. Even if they don't die they will go through a lot of stress and any injury or illness is likely to become very problematic. I would definitely look into a local source that uses parameters close to yours and not to your regional tap water.

I have definitely used the plop and drop method and I can definitely predict when I'm going to have problems. I would honestly only do this if you have a trusted source with matching parameters. There are so many things that can go wrong from disease to shock. I don't introduce my new fish directly to my display tanks, they get about a month of they're from a box store/ unknown origin or 2 weeks for trusted sources (though there's a handful of hobbyists that I break this rule for and introduce directly). I know it's excessive but it's saved me a lot in the long run.
 
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