Ro/Tap mix for breeding pair

Hi All,

Apologies if this has already been asked. I am looking for some confirmation around my approach for introducing a breeding pair to tap/RO mix SAFELY.

I have a breeding pair in a 3ft 220L tank (has been divided into two halves) on 100% tap water. I have managed to successfully hatch fry which are currently free swimming, but the hatch rate was very low. Lots of the eggs calcified, and the pair then ate them.

It is a well known fact that tap water around here is very hard. Out of the tap my PH is about 7.8 with a TDS of 280.

After doing some research I picked up an RODI filter unit, and I have successfully produced water at 0 TDS. I have not used any of the produce water yet.

Upon further research, it seems starting with a 50/50 mix of tap/RO is not a bad idea. I performed some tests by mixing 450ML of each in a 1L milk bottle. My results were as follows:

• 0 mins after mix - TDS 135 - PH 7.2
• 24 Hours after mix - TDS 135 - PH 7.2
• 48 Hours after mix - TDS 135 - PH 7.2

Ordinarally my aged tap water does not swing in PH, and this proves that my tap/RO mix also performs the same.

I was planning on doing a 50% WC with tap/RO mix, and continuing to WC with the tap/RO mix in future while the eggs are in the development phase preparing to hatch (hopefully yielding a much better hatch rate.)

My questions are as follows:

• Is a swing in PH from 7.8, to a final state PH of 7.2 too extreme? This would likely occur over 3-4 50% WC's
• Is there anything else I should consider, or may have over looked?

I am not chasing a specific PH here, though I do want to avoid PH crash and harming my pair. I am specifically chasing a lower TDS with the objective of having a higher hatch rate. The only other additive I use is Seachem prime water conditioner. I do not use anything else in my water. I simply heat it to 30deg C/86F and then WC.

Please let me know if you have any questions or need additional info. Appreciate all the advice.

Thank you

For optimal hatch rates, most believe a TDS of 70 - 80 is best. If you have been doing all the work with a specific purpose in mind, why have a TDS of 140ish?

I was more concerned about the safety of the approach. Obviously I could drop the TDS lower once I know 50/50 is safe, by using something like 70% RO/30% Tap.

You can put fish from hard water straight into R/O without any problems, except they'll perk up and the color will get a little better. I compete at shows which have pure R/O in the show tanks and the fish goes straight in with no problem.

Quote:

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Originally Posted by Willie

You can put fish from hard water straight into R/O without any problems, except they'll perk up and the color will get a little better. I compete at shows which have pure R/O in the show tanks and the fish goes straight in with no problem.

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Hi Willie. Thanks for that! Ill work on slowly adapting my breeding tank to around 80TDS for optimal hatch rate. Good to know that it is relatively low risk.

I believe that about 10 yrs ago I saw a video from Hans that showedhim putting eggs / cone in a glass vase with ro water to hatch them out. He left the vase in with the parents and put an air stone with them.

Quote:

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Originally Posted by twocat

I believe that about 10 yrs ago I saw a video from Hans that showedhim putting eggs / cone in a glass vase with ro water to hatch them out. He left the vase in with the parents and put an air stone with them.

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I often pull the spawn out and place it in an pitcher. My breeding tanks are glass so the handle of the pitcher can hook on to the outside of the tank leaving the pitcher inside of the aquarium. The breeding pair can see the eggs this keeps the pair in a breeding mode. If I have an egg eater pair once the fry are free swimming I can hand feed or pour the fry in with another breeding pair.

Cliff

Thanks for the advice all. I've managed to get 85 TDS water at a pH of 7.2 by mixing 120L RO/50L Tap in my barrel (70/30.) I'll look to continue water changes with this combo so the water conditions are stable for my pair. All the water in my breeding tank should turn over within a couple of water changes. Hopefully I will have more luck this time around :)

Quote:

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Originally Posted by Willie

You can put fish from hard water straight into R/O without any problems, except they'll perk up and the color will get a little better. I compete at shows which have pure R/O in the show tanks and the fish goes straight in with no problem.

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So you dont add minerals back to the RO water?

The amount of tap water he's using has plenty minerals in it.

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Originally Posted by aussietai

So you dont add minerals back to the RO water?

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Water in the Amazon has virtually no TDS, so no dissolved minerals. There is zero evidence that discus need minerals in the water to grow.

Willie and I agree that the fish get the minerals they need from their food.