Introducing RO water to existing tank

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JBFUK

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Hello,

I'm new to the forum and this is my first post.

Around a six weeks ago I brought a 40L 'Panorama' starter tank, upgraded U2 filter, added a 12w Chinese LED bar in addition to the supplied LED bar which seemed a bit weak. I believe the tank is fully cycled - master test kit results show 0-0.25 Ammonia, 0 NO2, 10-20 NO3. The Ammonia and NO2 results look very much the same as the tap water results, perhaps half a measure higher. Ph is around 7.5. I use Seachem prime/stability/pristine. I change 8-10L of water once per week. The tank houses 10 neons, 1 rummy nose, 1 ram, 3 otos and 2 wood shrimp with some plants in gravel.

I've been having problems with the water looking cloudy despite test results looking fine. Plants are also looking a bit sad/yellowing. They are fertilised with a couple of pumps of tropica liquid fert each week, and seachem tabs in the gravel.

Reading various articles and talking to the LFS it seems the only thing I can do to improve water quality further is to use RO water so that I can control PH and KH/GH. I understand this will suit the fish better (seem to prefer softer more acidic water) and may also help the plants with nutrient uptake. It would also mean that I'm not adding nitrates when adding new water. Based on that I have brought a 50 GPD 4-stage RODI and Seachem Equilibrium, Acid/Alkaline buffers. I also brought the API KH/GH test kit - KH is at 12 drops/dKH and GH at 18 drops (off the scale!). I don't fully understand the chart on the test kit instructions as I had thought GH had a measure of degrees rather than ppm.

So that's the background, now my questions:

How do I go about introducing RO water in to the tank and adjusting its parameters. I understand that the tank water parameters need to be adjusted gradually to avoid shocking the fish. Should I just start doing smaller water changes with pure RO and monitoring the Ph/KH/GH/TDS of the tank - then once it gets close to desired values begin to buffer the new water I put in there? If not then do I start to buffer the new water as per my desired target?

Should I mix the water with tap water to buffer or use the Seachem products to do this (I can easily return them to Amazon if I have mistakenly brought the wrong thing). Seems if I used tap water then I would be re-introducing some of the unwanted pollutants (like the nitrates) which partially defeats the point.

Are there other things I need to add to RO water in addition to the previously mentioned buffers? Seachem have such a range of additives and you read forums and people are adding phosphates, iron etc etc which gets to be a bit much to take in. If I use the buffers and continue using the tropica plant fert then will I be covered for all of the tanks needs? Perhaps there is and all-in-one buffer/mineral product that will set the water to the correct hardness and add all other required minerals?​


Having been bitten by the bug I just brought a 125L ROMA for our living room but want to get a handle on managing the smaller tank before I start to stock that with plants or fish.

I understand this is a complex topic and I have just dumped quite a few questions that may not have straightforward answers. Any advice will be appreciated.
 
It is a complex subject indeed - and probably not the cause of your cloudy water.
pH is not actually important to fish. This contradicts what most fish stores will tell you, the only thing that is important is that it is stable over time. The number that really matters is GH. So for example if you have 18dGH and wish to reduce it to 9dGH the easiest way is to mix RO water and tap water in the ratio 1:1. If your target is 6dGH you would go 2:1. Its a linear relationship.

Personally I would not add any other chemicals. Seachem Flourish Comprehensive supplement is the only thing I add for plants at half the recommended dose (even for my 2 tanks that use 100% RO). Most people suggest changing 50% of your water every week - personally I do 75%, even in my shrimp tank. The limiting factor in how low you cn let the GH go is your shrimp. I am not familiar with wood shrimp so you will have to look up their requirements.

When I switched to an RO mix I did daily 20% changes for a week using the target ratio and thereafter switched to large weekly changes also using the target ratio for the water changes.

Edit: While your NO3 is not ideal its not terrible if you keep up with regular large changes. Diluting it with RO means that this will naturally reduce anyway - also in a linear way.
 
Thanks seangee, lots of good information there. Although not what the instructions say, I take it I take it that 1 drop = 1 dGH for the GH test as with the KH test?

The wood shrimp is also known as the 'Bamboo Shrimp'. Looking up the recommended water parameters here (https://aquariumbreeder.com/bamboo-shrimp-detailed-guide-care-diet-and-breeding/) it seems like it would be okay with a KH & DH of 6 and PH of 7. I would like to keep Amano shrimp in my larger tank and they seem to have similar requirements (and it would be nice to keep the water parameters of each tank similar to make life easier, allow for quarantining in the smaller tank etc) .

Based on what you recommend I will mix approx 1/3 tap water with RO (will test before using) and start doing daily changes of 5-6L as the 40L tank but it only has 30-32L of water once water has been displaced by the filter, substrate, ornaments etc.

It would be nice to get the nitrate of the water going in to be 0 as I've read Otos are very sensitive to nitrates - I lost one a week ago for no apparent reason. I think I need to learn a lot more about the minerals and buffering before I do that. As you say mixing tap water with RO should still dilute it substantially.

Any other ideas on the cloudiness? It's a whiteish haze, could be some sort of bacterial bloom but I'm not sure how to deal with it other than a large water change. I guess we'll see when I start the daily changes. If I can get the RO filter hooked up and create enough RO water I may do the first one tonight. I last changed 10L on Monday morning and it certainly seems to have gotten more cloudy since then.
 
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Get yourself some (a lot) of jerry cans off amazon and anti-glug taps to go with them. The RO comes out pretty slowly. Last night and this morning I did the water change in my two smaller tanks and so far have only replaced 50 of the 70 liters I used :(. Still have to change the big tank tonight and that's another 120 litres.

I do use straight RO as my tapwater has 50ppm nitrates so even at 2:1 thats still too high. My tap water is 18dGH. I use salty shrimp GH/KH+ at the recommended dosage in my shrimp tank to get that up to 6dGH. Its way easier than the Seachem stuff (one spoon of a single powder per 10 litres) and does not make you water go yellow like the Seachem stuff I tried before.

I don't know about the API test. I got my results off Southern Water's website and the figure was confirmed by test strips.
 
The API testers are indeed 1 drop = 1 dH for both GH and KH. To convert to ppm, just multiply by 17.9 - or use the calculator on here (hover over How To Tips in the top menu bar and you'll find the Calculator at the bottom of the list)
Some fish profiles use dH and some use ppm, so you need GH in both units for researching fish.
 

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