Maybe the wrong place to post this, but I'll ask anyway!

[Chris918]

Hey guys and gals,

This is a saltwater forum and I'm aware of that. I started a freshwater tank as a side project this last week and went about fishless cycling. I use RODI water. I added Ammonium Chloride before adding my nitrifying bacteria like usual. I've done this with every reef tank I've ever set up. However, days later the ammonia is at the same concentration and I have 0 nitrites and 0 nitrates. I was informed by Dr Tim's that nitrifying bacteria can't live in RODI water since it has 0ppm TDS and said they couldn't help me. Is this true? I don't want to use tap water just so I can get a cycle started :/ Can anyone give me any recommendations?

Again I know this is a strange question, but this is the only forum I've ever used.

Thanks!

Chris

[Maggie321]

Do you have a filter? The bacteria should set up shop in there. Also on your substrate and any live plants you may have. I have fresh and salt... my fresh is heavily planted though. And I use tap water, not RODI. Is there a reason you are using RODI? I have heard of using TO for fish like discus, but what's the reason if I may ask?

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[Chris918]

I just want the cleanest possible water for my fish. Tap water can sometimes add phosphates, nitrates and other compounds or chemicals I don't want in my tank. RODI is the cleanest start possible and that's what I wanted for my freshwater aquarium just like my saltwater aquariums. Sadly, it seems that the bacteria can't thrive in this situation. I use RODI with saltwater too, but when mixing the salt you get a lot of additives like Calcium, Magnesium and other trace elements. Dr. Tim's said that bacteria can't live in a 0 TDS environment like the one I have so the cycle can't start. I just wanted to see if anyone else used RODI for freshwater.

[Jon0807]

I believe I've read somewhere that RODI is not good for freshwater fish because of the lack minerals.

[Chris918]

Yeah that must be somewhat true considering all the bacteria died in RODI.

[Maggie321]

It's incredibly rare for fresh water to be that clean. Minerals an stuff gets picked up in the dirt, rocks and stream bed. I have never tried it, but I would bet my shrimp tank that if you went to the clearest stream or lake you could find and brought a hand held TDS meter, it would NOT be 0. If you have a large sponge filter, with lots of surface area you may get something going. I wouldn't give up yet. I just don't see the benefit out weighing the trouble. They will, after all, be pooping in it. I use RODI for my saltwater as well. For the same reason but the only way I would use anything other than tap for my freshwater tank is if I was getting a fish that required it.

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[nereefpat]

I'm not surprised. It's not the lack of minerals. It's osmotic pressure. Cells can't live in RODI water.

Use tap. If you are worried about chlorine, for example, there are products to nuetralize that. You can also just aerate the water for a few hours, and it will be gone. Heavy metals can be filtered with carbon.

Nitrates and phoshates won't give you trouble, at least at the low amount that would be in your source water.

[Tripod1404]

If you really don’t want to use tap water, you can use bottled drinking water. But if your water is safe for human consumption, it won’t have any negative effects on fish. The only exception is if you want to keep shrimp or other inverts. I was never able to keep those with tap water. If you are going to make a planted tank, you would actually like nitrate and phosphate, otherwise you would need to dose those.


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[45commando]

I kept wild Discus ( Heckel & Tefe) for a couple of years before going back to reefing. They are the only fish I've seen that appear to thrive in very low TDS & very low pH water. Most freshwater species need at least some mineral content in the water for overall health & can adjust well to a very high mineral content.

The problem with low TDS water is a lack of buffering capacity, which can cause the pH to swing drastically between water changes. If the pH gets too low (in the 4s) then all bacterial function in the filters will cease. I ended up mixing my water change water 1/3 raw well water with 2/3 RO. This gave enough buffering capacity to hold the pH where I wanted it (low 6s). You'll have to play around with the ratios depending on what fish you want & what TDS/ KH your source water is. HTH

[otrips]

Here's the thing. RODI is not good for sustaining life due to the lack of minerals and other elements. The reason why it's ok using RODI in a saltwater system is that the Salt mix itself adds necessary minerals/elements. In a freshwater system because your not adding salt the water remains too pure.

[hkgar]

Part of setting up a salt water tank is the rock that becomes live rock. It is where the bacteria will start up housekeeping. It can also be done with sponges or other porous material but live rock and a sand substrate are best. If you read the startup threads you would learn the 1-2 pounds live rock per gallon is recommended.

[acsmith10]

I use RODI on my freshwater tank but add the 'good' minerals back in with Tropic Marin Re-Mineral Tropical. Hope this helps.


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[kenneth wolfe]

Cycling new tank in tap water is my preferred method it sterilizes the system then has lots of nutrients to jump start system, the thing is you have to wait, and do good water change of proper water, remember nothing good happens fast in reef tank even in start up, I've been know to pour strait vinegar in new tank to jump start bacteria growth , then change a majority of water after rocks ect have been seeded

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[Esterna]

It is important to cycle the water and clean the tank on regular basis. You can try using Penn Plax Cascade series canister filters which is very effective for the cleanliness of the fish tank and the health of fish. Check out https://itday.com/fish/penn-plax-cascade-series-canister-filter-reviews/ . You will get an ultimate buyer's guide on various filters.

[d0ughb0y]

I kept wild Discus ( Heckel & Tefe) for a couple of years before going back to reefing. They are the only fish I've seen that appear to thrive in very low TDS & very low pH water. Most freshwater species need at least some mineral content in the water for overall health & can adjust well to a very high mineral content.

The problem with low TDS water is a lack of buffering capacity, which can cause the pH to swing drastically between water changes. If the pH gets too low (in the 4s) then all bacterial function in the filters will cease. I ended up mixing my water change water 1/3 raw well water with 2/3 RO. This gave enough buffering capacity to hold the pH where I wanted it (low 6s). You'll have to play around with the ratios depending on what fish you want & what TDS/ KH your source water is. HTH

my brother used to breed discus and he only used RODI. So a blanket statement saying RODI is not for freshwater is not quite right.

[Sk8r]

honestly, look at where healthy freshwater fish live---over mud and rocks, grubbing for worms and such that thrive on poo. In my try at Tanganyika ciclids, after which I decided they were more trouble than a marine reef, I recall they had multiple bottles of additive minerals (read rock and mud) to make the tank as much as possible like that natural African lake...the waters of which you would not drink.

[kenneth wolfe]

honestly, look at where healthy freshwater fish live---over mud and rocks, grubbing for worms and such that thrive on poo. In my try at Tanganyika ciclids, after which I decided they were more trouble than a marine reef, I recall they had multiple bottles of additive minerals (read rock and mud) to make the tank as much as possible like that natural African lake...the waters of which you would not drink.Yep

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[hkgar]

There seems to be a sense that with saltwater tanks we keep our fish in 0 TDS water. Not at all true, just checked my tank and just as I thought TDS way high-488. We just start with 0 tds and then add a whole bunch more with the salt mix, but all good stuff and no bad.

[Small Heavens]

The beneficial bacteria needs dkh/alk and RODI water has zero of that. You can get bacteria for freshwater out of any pond, lake or even rain water puddles in some cases, but they would still need some added source of dkh/alkalinity.

[Green Chromis]

Here's the thing. RODI is not good for sustaining life due to the lack of minerals and other elements. The reason why it's ok using RODI in a saltwater system is that the Salt mix itself adds necessary minerals/elements. In a freshwater system because your not adding salt the water remains too pure.

:fish1: You can use RO water, in a freshwater system, just leave off the DI filtration, we had Discus for a long time in a 180gal freshwater planted system, and all the water was RO water, if you use RO/DI water you need to treat the water first to replenish the minerals and other things the DI filters take out. :fish1: