SW to FW conversion questions.

[NinnJinn]

I have had my 125 gallon DT with a 39 gallon sump saltwater system running for 3 years now.

I have had some hiccups along the way which I work through but due to the nearest SW store being 2 hours one way away from me and my online saltwater fish distributor being less-than-stellar with a lot of doa and the price almost tripling on SW fish I have decided to go the freshwater route.

I understand I will have to give the DT and sump a good cleaning along with filteration parts and things of the sort due to freshwater being freshwater and needing to remove all traces of salt.

To keep costs down and keep from soon-to-be wife from killing me I and wanting to use as much of my SW equipment as possible I had a few questions.


Do freshwater fish like water flow in the tank ex. Wavemakers?

the sump instead of having Chaetomorpha for saltwater use that area for Bio balls.
As for the bio balls, do I need to have a separate section to where there is very slow water flow? Or will the bio balls be able to work in high flow in the sump?

As for the Neptune Apex and Neptune dos can I continue to use that as a automatic water change at 10% total volume per day as I was doing with saltwater?

I have roughly 100 lb of Dry carb sea argonite still sealed in Factory packages, can I use that as a substrate in freshwater?

Also have a 5-stage Rodi system will that be okay for fish such as tetras and not sure the proper name but silver dollar fish along with a plecostimus and some guppies?

 

[Essjay]

Do freshwater fish like water flow in the tank ex. Wavemakers?

That depends. Fish from fast flowing streams do need a strong water flow, but fish from slow moving rivers and lakes need a slow water flow. Water flow is one of the factors we need to look at when deciding which fish to keep as it is better to have fish that all like the same.

I have roughly 100 lb of Dry carb sea argonite still sealed in Factory packages, can I use that as a substrate in freshwater?

Aragonite will increase hardness (GH). Unlike salt water fish, fresh water fish can come from hard water, soft water, or water in between. We should aim to keep fish which come from the same hardness as our tap water. And we should keep fish which all need the same hardness in the same tank.
Of the fish you name, tetras, silver dollars and plecs are soft water fish while guppies are hard water fish. The aragonite sand would be OK for the guppies but not the others.

As for the RO unit, that depends. If you have hard water and want to keep soft water fish, yes it would help to use all RO and add remineralisation salts back in or to mix RO and tap water to get the right hardness; RO also helps in regions which have high nitrate in tap water - again, if all RO is used, remineralisation salts would need to be added.
But if you have soft water and want to keep hard water fish, using RO would be pointless as you would need to add even more minerals than to soft tap water.

Something you need to do with freshwater fish is find out how hard your tap water is. The first place to check is your water provider's website. You need a number and the unit of measurement (there are several they could use). Then either match the fish to your tap water, or use RO for soft water fish if you have hard water, or add minerals to soft water if you want to keep hard water fish.



The best place for researching fresh water fish is https://www.seriouslyfish.com/knowledge-base/
This site will tell you the hardness and temperature a species needs; the size tank it needs; whether it needs fast or gently flowing water; and any personality habits that make it a bad match for other fish on your wish list.