diff --git a/src/fd_hz.erl b/src/fd_hz.erl
index 5ab6872..c19f7e9 100644
--- a/src/fd_hz.erl
+++ b/src/fd_hz.erl
@@ -13,6 +13,9 @@
     txs_of_height/1,
     mhs_of_height/1,
     txs_of_mh/1,
+    filter_spends/1,
+    filter_spend/1,
+    spend_info/1,
     test/0
 ]).
 
@@ -64,7 +67,7 @@ mhs_of_height(Height) ->
 
 txs_of_mh(MH) ->
     {ok, TXs} = hz:mb_txs(MH),
-    filter_spends(TXs).
+    TXs.
 
 
 filter_spends(TXs) ->
diff --git a/src/fd_spy.erl b/src/fd_spy.erl
index b2a97e1..32afeec 100644
--- a/src/fd_spy.erl
+++ b/src/fd_spy.erl
@@ -35,7 +35,8 @@
 -type search_pattern() :: #sp{}.
 
 -record(s,
-        {searching_for = [] :: search_pattern()}).
+        {last_height_seen = none :: none | integer(),
+         searching_for    = []   :: [search_pattern()]}).
 
 -type state() :: #s{}.
 
@@ -74,7 +75,7 @@ start_link() ->
 init(none) ->
     tell("starting fd_spy"),
     hz:chain_nodes(fewd:chain_nodes()),
-    hz:chain_nodes(fewd:chain_nodes()),
+    erlang:send_after(1000, self(), check_chain),
     InitState = #s{},
     {ok, InitState}.
 
@@ -104,6 +105,10 @@ handle_cast(Unexpected, State) ->
 
 
 
+handle_info(check_chain, State) ->
+    NewState = do_check_chain(State),
+    erlang:send_after(1000, self(), check_chain),
+    {noreply, NewState};
 handle_info(Unexpected, State) ->
     tell("~tp: unexpected info: ~tp", [?MODULE, Unexpected]),
     {noreply, State}.
@@ -124,6 +129,35 @@ terminate(_, _) ->
 %% internals
 %%-----------------------------------------------------------------------------
 
+do_check_chain(State = #s{last_height_seen = none}) ->
+    case hz:kb_current_height() of
+        {ok, Max} ->
+            hh(Max-1, Max, State);
+        Error     ->
+            tell("~tp hz error: ~tp", [?MODULE, Error]),
+            State
+    end;
+do_check_chain(State = #s{last_height_seen = Min}) ->
+    case hz:kb_current_height() of
+        {ok, Max} ->
+            hh(Min, Max, State);
+        Error     ->
+            tell("~tp hz error: ~tp", [?MODULE, Error]),
+            State
+    end.
+
+% handle height
+hh(PrevHeight, NewHeight, State) when PrevHeight < NewHeight ->
+    tell("~tp cool: PrevHeight=~tp, NewHeight=~tp", [?MODULE, PrevHeight, NewHeight]),
+    Spends = fd_hz:filter_spends(fd_hz:txs_from_to(PrevHeight + 1, NewHeight)),
+    tell("~tp spends: ~tp", [?MODULE, Spends]),
+    NewState = State#s{last_height_seen = NewHeight},
+    NewState;
+hh(PrevHeight, NewHeight, State) when PrevHeight >= NewHeight ->
+    log(info, "~tp lame: PrevHeight=~tp, NewHeight=~tp", [?MODULE, PrevHeight, NewHeight]),
+    State.
+
+
 -spec do_reg(Recipient, Amount, Payload, State) -> {Reply, NewState}
     when Recipient :: pubkey32(),
          Amount    :: pos_integer(),