picking hardness/ph

[Kendramc]

i'm getting an RO system soon, and am trying to figure out what hardness/ph i want to aim for.

i have a fully cycled 30 gal tank that will be down to 2 bristlenose plecos and a handful of java ferns when i start changing things. my tap water is a ph of around 7.5 (as per test strips) and very hard, so i have lots of room to play around, though the ph will stay about 7. i don't know what other fish i want to get in there yet, but it will be fairly standard, not livebearers that i can get at my local store. things that will go ok with my plecos.

with that in mind, what would you all suggest aiming for?

also, any fish suggestions to go with the numbers would be helpful.

thanks.

 

[Byron]

First, do you have the actual number for the GH? We have in the past had a number of situations where "very hard" turned out to actually be moderately hard/soft and even soft. The pH will follow the GH and KH, so I wouldnot mess with that, just get the GH on for the intended fish.

Which brings me to species...using straight RO is one option, if soft and very soft water fish are intended. The plecos would be OK, though knowing the species would help us just in case. All livebearers would be out, which seems to be to your liking anyway, and there are some other fish like some (but not all) of the rainbows that could manage in moderately hard...it really all depends upon species, and how much work you want to put into this. And expense...I had basically pure water out of my tap for all my 30 years of fishkeeping but I understand that RO does waste water, so this may be important for monetary reasons (if on a meter) as well as environmental. You need to have the water prepared with the same parameters as the tank water for every water change, another extra bit of work depending how you look at it.

 

[Kendramc]

do you have the actual number for the GH?

my gh and kh both max out the test strips, so >180 gh and >240 kh. i don't have exact numbers, and my city water doesn't report hardness. i've checked.

plecos would be OK, though knowing the species would help us just in case

they are bristlenoses.

using straight RO is one option

i'd rather not do straight RO (i've read mixed information on whether doing so is a good idea, and i don't think it is necessary). i plan to mix it with my tap water, just trying to figure out my ratios. the extra work doesn't worry my, i figure i'll prep it in buckets ahead of time since i don't want to put too much water through the system in one day anyway.

 

[Byron]

You will need a good test for both GH and KH (and pH obviously) if you do go down this road of adjusting parameters. I've done it twice, in my three decades, for the opposite reason--increasing GH and pH. I used the API liquid test (GH/KH) and other members can suggest other brands of reliable tests.

Mixing RO and tap water is proportional. It depends upon the exact GH of the tap. Mixing 50/50, as one example, would reduce the GH by half. So you need to know the end number you want in order to proportionally mix the waters. The KH and pH will follow. The level of KH especially will determine the extent to which the pH will lower. I don't think there is any magic formula for this, it all depends upon the initial GH, KH and pH, and the proportion you decide upon.

As for straight RO, this is another of those silly myths that are too common in this hobby. Several members here have used straight RO to get very soft water, @seangee is one who comes to mind, and he can certainly confirm it had/has no issues whatsoever. I know that Ian Fuller who is the authority on the Corydoradinae uses straight RO for breeding and long-term maintenance. To my mind, it is far less risk than mixing, but that is for you to decide. I just want to explode the nonsense out there.

 

[Kendramc]

You will need a good test for both GH and KH (and pH obviously) if you do go down this road of adjusting parameters

oh, yes, i fully intend to once i get the system set up, it just hasn't seemed necessary up to this point. i'm just trying to figure out what some reasonable goals would be.

i know i have a lot of work to do before things are finalized, but i have some time. if nothing else, i have to slowly change the water that is in the tank right now to avoid stressing my plecos too much. really don't want to upset them any more than is necessary.

 

[10 Tanks]

Hello. I can see a possible benefit by using RO water, because you don't need a water treatment to remove everything that's put into tap water to make it safe to drink. But, what about all the minerals in tap water that help maintain a steady water chemistry? RO water is missing all those minerals. The water chemistry would be unsteady and would be a problem for your fish. Maybe this water could be used to top off a tank between water changes.

10 Tanks (Now 11)

 

[seangee]

oh, yes, i fully intend to once i get the system set up, it just hasn't seemed necessary up to this point. i'm just trying to figure out what some reasonable goals would be.

i know i have a lot of work to do before things are finalized, but i have some time. if nothing else, i have to slowly change the water that is in the tank right now to avoid stressing my plecos too much. really don't want to upset them any more than is necessary.

Don't bother with targets for pH - it will be what it will be. I only target GH and KH where appropriate. In my tanks:

1. Straight RO for very soft water fish, GH=KH=0 and pH 5, can't measure this with normal fish equipment and there is a lot of wood and leaf litter in this tank, plants in this tank do fine but only acid loving plants - many plants from my other tanks do not work in here.
2. dGH = 3, KH = 0, pH = 6.8. Also softwater fish but not super soft water. I used to run this with straight RO but the plants do better with some supplements, so I have recently been adding this. Some of the plants that grow in tank #1 won't grow here
3. dGH = 3, dKH = 0, pH = 6.0. Similar to tank #2 and relatively similar stocking and planting levels. I cannot account for the pH difference and won't try - one tank is 200l and the other is 70l
4. dGH = 6, dKH =3, pH = 7.0 This one has red cherry shrimps as well as fish that prefer less soft water.

For tanks 2&3 I use Bee Shrimp mineral GH+, this is a one shot and I simply add one scoop per 20l of water. For tank #4 I use Salty Shrimp GH/KH+ and one scoop per 10l. I really can't be bothered with products like Seachem where they require you to buy multiple products and test to find the correct ratios - I have tested these and they provide exactly what they say. Brands may of course be different in the US.
I don't mix with tap water because my tap water contains nitrates at 50ppm.

I don't know if this applies to all plecs but my bristelnose spent the first 13 years of his life in my tap water (which is hard enough that you can walk on it), and the next 6 in tank #2, so they are super tolerant of water conditions. And yes - he really did live 19 years.

I typically change around 75% of the water per week.
This is tank #1 - in case you are put off by my plant comments - and its chemistry has not changed in the 3 years its been running. Tank #2 is my signature.

 

[Byron]

Hello. I can see a possible benefit by using RO water, because you don't need a water treatment to remove everything that's put into tap water to make it safe to drink. But, what about all the minerals in tap water that help maintain a steady water chemistry? RO water is missing all those minerals. The water chemistry would be unsteady and would be a problem for your fish. Maybe this water could be used to top off a tank between water changes.

10 Tanks (Now 11)

It may be a different understanding of the terms... but a stable water chemistry is due to the water parameters, replenished with water changes using the same-parameter water. RO water would be zero GH and KH, and the pH would be acidic though at different levels depending upon what is in the tank, which means anything inclined to dissolved calcium (limestone, shells, etc), and any dead organics which includes the fish being fed, wood, dried leaves.

Given that the majority of aquarium fish from South America and SE Asia live their lives in water with zero GH and KH and an acidic pH, they will not have need for minerals beyond what they eat. There are other species from different parameter natural waters which are a different story.

And as seangee noted concerning the plants, most of us would provide some mineral nutrients for the plants, though the level of these entering the fish is I would expect very, very low.

 

[Colin_T]

Angelfish, discus, most tetras, most barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH below 150ppm and usually below 100ppm) and a pH below 7.0.

Livebearers (guppies, platies, swordtails, mollies), rainbowfish and goldfish occur in medium hard water with a GH around 180-250ppm (250ppm+ for mollies) and a pH above 7.0.

If you have very hard water (GH above 300ppm) then look at African Rift Lake cichlids.

 

[Fishmanic]

I love my tiger barb/ black skirt tetra/ pleco tank. You might consider them.

 

[Kendramc]

Angelfish, discus, most tetras, most barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH below 150ppm and usually below 100ppm) and a pH below 7.0.

this is exactly what i was looking for, thank you.

not to slight what others have told me, there has been a lot of helpful info in here, this sentence was just a very concise answer.