Joining New and Existing Tank to New larger sump?

So I'm planning on starting a new 125g tank, and was curious if my old 75g tank could use the new sump as well given it be big enough for both tanks I was thinking at least a 100g sump, just to reduce the maintenance Id have to do on two separate sumps, with the new tank having to cycle and all, even after I dont see any opportunity to switch over the 75 to the new sump without effecting the levels in the 75. What do you guys think about this, or would it just be a waste of time?

 

Thats going to be tricky cause the 75 would have to be feeding both tanks and a skimmer large enough for 2 tanks. Also think about if the power ever goes out you are going to have to have enough room in just one sump for that water to drain into.

IMO i would do 2 sumps just to make things easy.

 

It could be done, but it will just be more difficult than it would be if the tanks were smaller. I think a 100g sump would be big enough for 200 gallons of water (display tanks). maybe even a 75g sump.

Just be sure that the sump has a big enough footprint to accommodate any thing you nay want: return, reactors (hang on or in the water - maybe next to sump), skimmer, refugium, ATS, live rock section, etc.

As far as the water parameters - that's why it's tricky. How close are the two tanks in water chemistry? What are the parameters in each tank?

 

Water chemistry is what I would really be worried about especially starting a new tank and joining a old tank might cause a cycle and your params to swing in a dramatic way MAYBE.

 

When you say "new" 125g..do you mean it was set up recently? Or does it not have water in it yet?

 

You can have two displays off the same sump. That is no problem. You can have sump -> 125 -> 75 -> sump or sump -> 125 -> sump and sump -> 75 -> sump. In the second example you need two return pumps though, and your skimmer from the 75 probably isn't big enough for all the new water volume. So, it will expand your water volume, but probably won't save you much money, as you'll still need new equipment. You'd just have 1 less sump.

As to cycling. You can add all the water volume right away without causing a cycle. The biofilter capacity is based on bioload, not water-volume. So, you can add as much water as you want without issue, if the parameters are matched. Where you'll get into trouble is if you add livestock too quickly. However, if you keep your existing livestock, and add new livestock slowly, you should never see a cycle in the new system if the tanks are tied together.

 

No I'm just in process of buying it so brand new

 

Not close at all, I'm getting everything for the 125 this weekend so one brand new and one existing tank,

 

So should I keep my existing sump and add a new one onto everything? Can I jut add water to my 75 set up an have it run through to the 125 and it's sump, I can avoid a cycle like that right?

 

That is exactly what I was getting at. Use the sump you have now. When you get the new tank, just tie the plumbing in with our current sump. Water parameters should take on those paramaters (though some such as nitrates/trites/phosphates will be diluted, due to the added water volume) of the old tank.